Method, apparatus and program for recording and playing back content data, method, apparatus and program for playing back content data, and method, apparatus and program for recording content data

ABSTRACT

A method, apparatus and program for recording and playing back content data, method, apparatus and program for playing back content data, and method, apparatus and program for recording content data. The recording and playback apparatus is configured to record content data including a content and play back the content of the content data at a position specified by first relative time information indicating a relative time with respect to a start position of the content. A record start time information generator generates record start time information. A stream playback control table generator generates a stream playback control table associated with a stream resource record in a content data recording unit. Based on the content start time information and the record start time information, a relative time information correction unit corrects relative time information, of a segment to be played back, identified by a metadata manager based on segment metadata. A read controller controls a reading process according to the relative position information corresponding to the corrected relative time information identified by the metadata manager.

CROSS REFERENCES TO RELATED APPLICATIONS

The present application claims priority to Japanese Patent ApplicationNo. 2004-282215 filed in the Japan Patent Office on Sep. 28, 2004, theentire contents of which being incorporated herein by reference.

BACKGROUND

The present invention relates to a method, apparatus and program forrecording and playing back content data, a method, apparatus and programfor playing back content data, and a method, apparatus and program forrecording content data. More particularly, the present invention relatesto a method, apparatus and program for recording and playing backcontent data, a method, apparatus and program for playing back contentdata, and a method, apparatus and program for recording content datathat make it possible for a user to view a specified content in a highlyreliable fashion.

In recent years, a digital broadcast service provided by a broadcaststation by transmitting a digital television signal has become popular.In digital broadcast services, because a broadcast television signal isin the form of digital data, it is easy to process the televisionsignal. Therefore, if a broadcast station supplies metadata togetherwith a content, a television receiver not only can simply output thereceived content but also can process the received content in variousways.

For example, many methods have been proposed to transmit, together witha program (content), information associated with the program to providevarious kinds of services such as electronic program guide information,a program index, subtitles, sub audio information (for vision-impairedusers), supplementary program information (indicating, for example,performers or the like, a summary of a program, etc.), a multiviewtelevision image (using a plurality of cameras located at differentpositions), and/or an interactive program (a shopping program, aquestionnaire program, etc.) as disclosed, for example, in JapaneseUnexamined Patent Application Publication No. 2002-176401.

A method has been proposed to control information associated with imageobjects multiplexed on a data channel so as to display image objects ina superimposed manner in synchronization with video/audio datamultiplexed on a video/audio channel of a digital broadcast program sothat if an image object is selected, the program is controlled inaccordance with information associated with the selected image object asdisclosed, for example, in Japanese Unexamined Patent ApplicationPublication No. 2002-185885.

A method has also been proposed to provide sub-information associatedwith a particular image object in a television program image such that aviewer can easily acquire sub-information via link data as disclosed,for example, in Japanese Unexamined Patent Application Publication No.2003-259336.

Furthermore, not only associated data is simply added to a mainbroadcast program data (content data) as in the above-describedtechniques, but a method has been proposed to control a programreceiving mode or a program display mode by additional sub-data.

For example, it has been proposed to record, in a television receiver, aprogram (program) broadcast from a broadcast station and play backspecified one or more units or scenes (segments) of the recorded programin accordance with a request issued by a user. This type of broadcastservice is known as server-type broadcasting. In this technique, forexample, a broadcast station provides, in addition to program data,segment metadata indicating an attribute of segments and the relativetime of each segment with respect to the start of the program to atelevision receiver. The television receiver acquires the segmentmetadata as well as the program data (content data) and plays back aparticular segment based on the segment metadata.

FIG. 1 shows an example of an example of a known method of extracting asegment. As shown in a lower area of FIG. 1, a television receiverreceives segment metadata 11 as well as a stream resource 1 in theMPEG2-TS (Moving Picture Experts Group 2-Transport Stream) format asprogram data. When the television receiver records the stream resource1, the television receiver produces a stream playback control table 12indicating the correspondence between relative time informationindicating a temporal position as measured from a start of the streamresource 1 and relative position information indicating a data positionas measured from the start of the stream resource 1, for picture (frame)data of the stream resource 1, as represented by dashed line 21. In thisprocess of generating the stream playback control table 12, thetelevision receiver generates elements of the stream playback controltable 12 in units of GOPs (Group Of Pictures) (such that relativetime/position information indicates the time/position of the firstpicture of each GOP).

If a user specifies attribute information corresponding to an ID of “n”(attribute information associated with a segment N) in the segmentmetadata 11 (as shown by an arrow 22), the television receiveridentifies relative time information Tsegn corresponding to thespecified attribute information. The television receiver furtheridentifies relative position information Dsegn corresponding to theidentified relative time information Tsegn, based on the stream playbackcontrol table 12 (as shown by an arrow 23). Based on the identifiedrelative position information Dsegn, the television receiver accessesthe stream resource 1 to read the specified segment N.

The television receiver does not necessarily always operate insynchronization with broadcast processing performed by a broadcaststation. In digital broadcasting, the television receiver generallycontrols the processing timing in accordance with a time offset table(TOT) that is a clock signal supplied from a broadcast station. Forexample, when automatic recording of a program is programmed, thetelevision receiver detects the current time based on the TOT and startsthe recording operation when the current time reaches the programmedrecord start time.

However, the accuracy of the TOT is not high enough to precisely controlthe broadcast timing in units of frames. For example, depending on theradio wave propagation condition, as great a shift in the broadcasttiming as a few seconds from an intended start time can occur. In theconventional television receiver, because the recording timing iscontrolled based on the time information with such low accuracy, it isdifficult to start recording exactly synchronously with the start of abroadcast program. Furthermore, in the television receiver, there is apossibility that a delay occurs in receiving or recording of a programdue to an event of an interrupt.

For the above-described reasons, it is sometimes difficult for thetelevision receiver to start recording of a program (a broadcastcontent) specified to be recorded precisely from the start of theprogram and it is also difficult to end the recording precisely at theend of the program. For example, when a program is set to beautomatically recorded in accordance with an electronic program guide(EPG), the television receiver starts recording of the program at thepredetermined start time. However, there is a possibility that therecording of the program starts before or after the actual start of theprogram, a shift can occur between the start of the recorded data andthe start of the program. Furthermore, for the same reasons, there is apossibility that the recording of the program is ended before or afterthe actual end of the program.

Thus, if playback of data is controlled by the above-described method,there is a possibility that a shift occurs between the relative timeinformation (relative time information indicating the start position ofa program) described in the segment metadata 11 supplied from abroadcast station and the relative time information (relative timeinformation with respect to the start position of the recorded streamresource 1) described in the generated stream playback control table 12.If the data is read in accordance with the relative position informationobtained in the above-described situation, there is a possibility thatthe playback of the segment N is started before or after the correctstart position or the playback is ended before or after the correct endposition. That is, there is a possibility that the specified segment Nis not correctly played back.

SUMMARY

In view of the above, the present invention provides a technique ofplaying back a content more precisely such that the playback starts fromthe exact start position and ends at the exact end position therebyensuring that a user can view the specified content.

More specifically, a recording and playback apparatus according to anembodiment of the present invention includes first recording means forrecording the content data, record start time information generationmeans for generating, using reference time information, record starttime information indicating time information associated with a recordstart position of the content data recorded by the first recordingmeans, playback control table generation means for generating a playbackcontrol table indicating, for a particular part of the content datarecorded by the first recording means, correspondence between secondrelative time information indicating a relative time with respect to therecord start position of the content data and the amount of the contentdata as measured from the record start position, second recording meansfor recording playback control information including content start timeinformation indicating the content start position using the referencetime information, the record start time information generated by therecord start time information generation means, and the playback controltable generated by the playback control table generation means, playbackcontrol information reading means for reading the content start timeinformation, the record start time information, and the playback controltable recorded by the second recording means, relative time informationcorrection means for correcting the first relative time informationspecifying a playback position of the content data, based on the contentstart time information and the record start time information read by theplayback control information reading means, so as to acquire the secondrelative time information, identification means for identifying therelative position information of the playback position, based on thesecond relative time information acquired via the correction made by therelative time information correction means using the playback controltable read by the playback control information reading means, andplayback means for playing back the contend data by reading the contentdata at the playback position corresponding to the relative positioninformation identified by the identification means.

The recording and playback apparatus may further include receiving meansfor receiving the content data and the content start time informationbroadcast by a broadcast station.

The recording and playback apparatus may further include communicationmeans for communicating with another apparatus to acquire the contentdata and the content start time information transmitted from thatapparatus.

The recording and playback apparatus may further include output meansfor outputting the content data played back by the playback means.

The content data may be in a form compressed according to the MPEGstandard, the playback control table generation means may generate theplayback control table indicating the correspondence between the secondrelative time information and the relative position information for afirst picture of each GOP of the content data, and, based on theplayback control table, the identification means may redefine theplayback position at the first picture of a GOP including the playbackposition and may identify the relative position information of the firstpicture.

The content data may be in a form encrypted according to a predeterminedmethod, and the recording and playback apparatus may further includedecoding means for decoding the encrypted content data, and playbackposition setting means for setting the playback position such that theplayback position provides a period of time equal to or longer than aperiod of time necessary for the decoding means to complete the processof decoding the encrypted content data.

A recording and playback method according to an embodiment of theinvention includes the steps of recording the content data, generating,using reference time information, record start time informationindicating time information associated with a record start position ofthe content data recorded in the content data recording step, generatinga playback control table indicating, for a particular part of thecontent data recorded in the content data recording step, correspondencebetween second relative time information indicating a relative time withrespect to the record start position of the content data and the amountof the content data as measured from the record start position,recording playback control information including content start timeinformation indicating the content start position using the referencetime information, the record start time information generated in therecord start time information generation step, and the playback controltable generated in the playback control table generation step, readingthe content start time information, the record start time information,and the playback control table recorded in the playback controlinformation recording step, correcting the first relative timeinformation specifying a playback position of the content data, based onthe content start time information and the record start time informationread in the playback control information reading step, so as to acquirethe second relative time information, identifying the relative positioninformation of the playback position, based on the second relative timeinformation acquired in the relative time information correction stepusing the playback control table read in the playback controlinformation reading step, and playing back the contend data by readingthe content data at the playback position corresponding to the relativeposition information identified in the identification step.

A program according an embodiment of the present invention includes thesteps of recording the content data, generating, using reference timeinformation, record start time information indicating time informationassociated with a record start position of the content data recorded inthe content data recording step, generating a playback control tableindicating, for a particular part of the content data recorded in thecontent data recording step, correspondence between second relative timeinformation indicating a relative time with respect to the record startposition of the content data and the amount of the content data asmeasured from the record start position, recording playback controlinformation including content start time information indicating thecontent start position using the reference time information, the recordstart time information generated in the record start time informationgeneration step, and the playback control table generated in theplayback control table generation step, reading the content start timeinformation, the record start time information, and the playback controltable recorded in the playback control information recording step,correcting the first relative time information specifying a playbackposition of the content data, based on the content start timeinformation and the record start time information read in the playbackcontrol information reading step, so as to acquire the second relativetime information, identifying the relative position information of theplayback position, based on the second relative time informationacquired in the relative time information correction step using theplayback control table read in the playback control information readingstep, and playing back the contend data by reading the content data atthe playback position corresponding to the relative position informationidentified in the identification step.

A playback apparatus according to an embodiment of the present inventionincludes playback control information reading means for reading, from arecording medium, content start time information indicating, usingreference time information, time information associated with a startposition of a content, record start time information indicating, usingthe reference time information, time information associated with arecord start position of the content data, and a playback control tableindicating, for a particular part of the content data recorded on therecording medium, correspondence between second relative timeinformation indicating a relative time with respect to the record startposition of the content data and the amount of the content data asmeasured from the record start position, relative time informationcorrection means for correcting the first relative time informationspecifying a playback position of the content data, based on the contentstart time information and the record start time information read by theplayback control information reading means, so as to acquire the secondrelative time information, identification means for identifying therelative position information of the playback position, based on thesecond relative time information acquired via the correction made by therelative time information correction means using the playback controltable read by the playback control information reading means, andplayback means for playing back the contend data by reading the contentdata at the playback position corresponding to the relative positioninformation identified by the identification means.

The playback apparatus may further include output means for outputtingthe content data played back by the playback means.

In the playback apparatus, the content data may be in a form compressedaccording to the MPEG standard, and, based on the playback control tableindicating the correspondence between the second relative timeinformation and the relative position information for the first pictureof each GOP of the content data, the identification means may redefinethe playback position at the first picture of a GOP including theplayback position and may identify the relative position information ofthe first picture.

In the playback apparatus, the content data may be in a form encryptedaccording to a predetermined method, and the playback apparatus mayfurther include decoding means for decoding the encrypted content data,and playback position setting means for setting the playback positionsuch that the playback position provides a period of time equal to orlonger than a period of time necessary for the decoding means tocomplete the process of decoding the encrypted content data.

A playback method according to an embodiment of the present inventionincludes the steps of reading, from a recording medium, content starttime information indicating, using reference time information, timeinformation associated with a start position of a content, record starttime information indicating, using the reference time information, timeinformation associated with a record start position of the content data,and a playback control table indicating, for a particular part of thecontent data recorded on the recording medium, correspondence betweensecond relative time information indicating a relative time with respectto the record start position of the content data and the amount of thecontent data as measured from the record start position, correcting thefirst relative time information specifying a playback position of thecontent data, based on the content start time information and the recordstart time information read in the playback control information readingstep, so as to acquire the second relative time information, identifyingthe relative position information of the playback position, based on thesecond relative time information acquired in the relative timeinformation correction step using the playback control table read in theplayback control information reading step, and playing back the contenddata by reading the content data at the playback position correspondingto the relative position information identified in the identificationstep.

A program according to an embodiment of the present invention includesthe steps of reading, from a recording medium, content start timeinformation indicating, using reference time information, timeinformation associated with a start position of a content, record starttime information indicating, using the reference time information, timeinformation associated with a record start position of the content data,and a playback control table indicating, for a particular part of thecontent data recorded on the recording medium, correspondence betweensecond relative time information indicating a relative time with respectto the record start position of the content data and the amount of thecontent data as measured from the record start position, correcting thefirst relative time information specifying a playback position of thecontent data, based on the content start time information and the recordstart time information read in the playback control information readingstep, so as to acquire the second relative time information, identifyingthe relative position information of the playback position, based on thesecond relative time information acquired in the relative timeinformation correction step using the playback control table read in theplayback control information reading step, and playing back the contenddata by reading the content data at the playback position correspondingto the relative position information identified in the identificationstep.

A recording apparatus according to an embodiment of the presentinvention includes first recording means for recording the content data,record start time information generation means for generating, usingreference time information, record start time information indicatingtime information associated with a record start position of the contentdata recorded by the first recording means, playback control tablegeneration means for generating a playback control table indicating, fora particular part of the content data recorded by the first recordingmeans, correspondence between second relative time informationindicating a relative time with respect to the record start position ofthe content data and the amount of the content data as measured from therecord start position, second recording means for recording playbackcontrol information including content start time information indicatingthe content start position using the reference time information, therecord start time information generated by the record start timeinformation generation means, and the playback control table generatedby the playback control table generation means.

The recording apparatus may further include receiving means forreceiving the content data and the content start time informationbroadcast by a broadcast station.

The recording apparatus may further include communication means forcommunicating with another apparatus to acquire the content data and thecontent start time information transmitted from that apparatus.

A recording method according to an embodiment of the present inventionincludes the steps of recording the content data, generating, usingreference time information, record start time information indicatingtime information associated with a record start position of the contentdata recorded in the content data recording step, generating a playbackcontrol table indicating, for a particular part of the content datarecorded in the content data recording step, correspondence betweensecond relative time information indicating a relative time with respectto the record start position of the content data and the amount of thecontent data as measured from the record start position, and recordingplayback control information including content start time informationindicating the content start position using the reference timeinformation, the record start time information generated in the recordstart time information generation step, and the playback control tablegenerated in the playback control table generation step.

A program according to an embodiment of the present invention includesthe steps of recording the content data, generating, using referencetime information, record start time information indicating timeinformation associated with a record start position of the content datarecorded in the content data recording step, generating a playbackcontrol table indicating, for a particular part of the content datarecorded in the content data recording step, correspondence betweensecond relative time information indicating a relative time with respectto the record start position of the content data and the amount of thecontent data as measured from the record start position, recordingplayback control information including content start time informationindicating the content start position using the reference timeinformation, the record start time information generated in the recordstart time information generation step, and the playback control tablegenerated in the playback control table generation step.

A recording and playback apparatus according to an embodiment of thepresent invention includes first recording means for recording thecontent data, record start time information generation means forgenerating, using reference time information, record start timeinformation indicating time information associated with a record startposition of the content data recorded by the first recording means,second recording means for recording playback control informationincluding content start time information indicating the content startposition using the reference time information, the record start timeinformation generated by the record start time information generationmeans, and a playback control table indicating, for a particular part ofthe content data recorded by the first recording means, correspondencebetween the relative time information and first relative positioninformation indicating the amount of data as measured from the start ofthe content, playback control information reading means for reading thecontent start time information, the record start time information, andthe playback control table recorded by the second recording means,offset value calculation means for calculating an offset value to beused in correction of the first relative position information, using thecontent start time information, the record start time information, andthe playback control table read by the playback control informationreading means, identification means for identifying the first relativeposition information associated with the playback position specified bythe relative time information, based on the playback control table readby the playback control information reading means, relative positioninformation correction means for correcting the first relative positioninformation identified by the identification means, based on the offsetvalue calculated by the offset value calculation means, to acquire thesecond relative position information indicating the amount of data asmeasured from the record start position of the content data recorded bythe first recording means, and playback means for playing back thecontent data by reading the content data at the playback position, basedon the second relative position information acquired via the correctionprocess performed by the relative position information correction means.

A recording and playback method according to an embodiment of thepresent invention includes the steps of recording the content data,generating, using reference time information, record start timeinformation indicating time information associated with a record startposition of the content data recorded in the content data recordingstep, recording playback control information including content starttime information indicating the content start position using thereference time information, the record start time information generatedin the record start time information generation step, and a playbackcontrol table indicating, for a particular part of the content datarecorded in the content data recording step, correspondence between therelative time information and first relative position informationindicating the amount of data as measured from the start of the content,reading the content start time information, the record start timeinformation, and the playback control table recorded in the playbackcontrol information recording step, calculating an offset value to beused in correction of the first relative position information, using thecontent start time information, the record start time information, andthe playback control table read in the playback control informationreading step, identifying the first relative position informationassociated with the playback position specified by the relative timeinformation, based on the playback control table read in the playbackcontrol information reading step, correcting the first relative positioninformation identified in the identification step, based on the offsetvalue calculated in the offset value calculation step, to acquire thesecond relative position information indicating the amount of data asmeasured from the record start position of the content data recorded inthe content data recording step, and playing back the content data byreading the content data at the playback position, based on the secondrelative position information acquired in the relative positioninformation correction step.

A program according to an embodiment of the present invention includesthe steps of recording the content data, generating, using referencetime information, record start time information indicating timeinformation associated with a record start position of the content datarecorded in the content data recording step, recording playback controlinformation including content start time information indicating thecontent start position using the reference time information, the recordstart time information generated in the record start time informationgeneration step, and a playback control table indicating, for aparticular part of the content data recorded in the content datarecording step, correspondence between the relative time information andfirst relative position information indicating the amount of data asmeasured from the start of the content, reading the content start timeinformation, the record start time information, and the playback controltable recorded in the playback control information recording step,calculating an offset value to be used in correction of the firstrelative position information, using the content start time information,the record start time information, and the playback control table readin the playback control information reading step, identifying the firstrelative position information associated with the playback positionspecified by the relative time information, based on the playbackcontrol table read in the playback control information reading step,correcting the first relative position information identified in theidentification step, based on the offset value calculated in the offsetvalue calculation step, to acquire the second relative positioninformation indicating the amount of data as measured from the recordstart position of the content data recorded in the content datarecording step, and playing back the content data by reading the contentdata at the playback position, based on the second relative positioninformation acquired in the relative position information correctionstep.

In the recording and playback apparatus, the recording and playbackmethod, and the program according to an embodiment of the presentinvention, content data is recorded, record start time informationindicating, using the reference time information, time informationassociated with a record start position of the content data isgenerated, a playback control table is generated to represent, for aparticular part of the recorded content data, correspondence betweensecond relative time information indicating a relative time with respectto the record start position of the content data and the amount of thecontent data as measured from the record start position, content starttime information indicating the content start position using thereference time information, record start time information and theplayback control table are recoded as playback control information, thecontent start time information, the record start time information, andthe playback control table recorded in the playback control informationare read, the first relative time information specifying the playbackposition of the content data is corrected based on the content starttime information and the record start time information so as to acquirethe second relative time information, the relative position informationof the playback position is identified based on the second relative timeinformation using the playback control table, and reading the contentdata at the playback position corresponding to the identified relativeposition information thereby playing back the content data.

In the playback apparatus, the playback method, and the programaccording to an embodiment of the invention, content start timeinformation indicating, using reference time information, timeinformation associated with a start position of a content, record starttime information indicating, using the reference time information, timeinformation associated with a record start position of the content data,and a playback control table indicating, for a particular part of thecontent data recorded on the recording medium, correspondence betweensecond relative time information indicating a relative time with respectto the record start position of the content data and the amount of thecontent data as measured from the record start position are read from arecording medium. The second relative time information is acquired bycorrecting the first relative time information specifying a playbackposition of the content data, based on the content start timeinformation and the record start time information. Using the playbackcontrol table, the relative position information of the playbackposition is identified based on the corrected second relative timeinformation. The contend data at the playback position corresponding tothe identified relative position information is read and played back.

In the recording apparatus, the recording method, and the programaccording to an embodiment of the present invention, content data isrecorded, record start time information indicating time informationassociated with a record start position of the content data is generatedusing reference time information, and a playback control table isgenerated to represent, for a particular part of the recorded contentdata, correspondence between second relative time information indicatinga relative time with respect to the record start position of the contentdata and the amount of the content data as measured from the recordstart position. Furthermore, control information including content starttime information indicating the content start position using thereference time information, the record start time information, and theplayback control table are recorded as playback control information.

In the recording and playback apparatus, the recording and playbackmethod, and the program according to an embodiment of the presentinvention, content data is recorded, and record start time informationindicating time information associated with a record start position ofthe content data is generated using reference time information.Furthermore, control information including content start timeinformation indicating the content start position using the referencetime information, the record start time information, and a playbackcontrol table indicating, for a particular part of the content data,correspondence between the relative time information and first relativeposition information indicating the amount of data as measured from thestart of the content are recorded. The content start time information,the record start time information, and the playback control table areread, and an offset value to be used in correction of the first relativeposition information is calculated using the content start timeinformation, the record start time information, and the playback controltable. The first relative position information associated with theplayback position specified by the relative time information is thenidentified based on the playback control table, and the identified firstrelative position information is corrected using the offset value toacquire the second relative position information indicating the amountof data as measured from the record start position of the content data.Finally, the content data is played back by reading the content data atthe playback position, based on the corrected second relative positioninformation.

Thus, the present invention provides the great advantage that a contentspecified by a user is precisely played back such that the user can viewthe exact specified content.

Additional features and advantages are described herein, and will beapparent from, the following Detailed Description and the figures.

BRIEF DESCRIPTION OF THE FIGURES

FIG. 1 is diagram showing an example of a known method of extracting asegment.

FIG. 2 is a block diagram showing a digital broadcast televisionreceiver according to an embodiment of the present invention.

FIG. 3 is a block diagram showing an example of a detailedimplementation of a system controller shown in FIG. 2.

FIG. 4 shows an example of a format of content metadata shown in FIG. 3.

FIG. 5 shows an example of a format of segment metadata shown in FIG. 3.

FIG. 6 shows an example of a format of a stream playback control tableshown in FIG. 3.

FIG. 7 shows an example of a format of associated data shown in FIG. 3.

FIG. 8 is a diagram showing a process of receiving a television signalof a program broadcast from a broadcast station and recording theprogram.

FIG. 9 is a diagram showing a segment playback process.

FIG. 10 is a flow chart showing a process of receiving and recording acontent.

FIG. 11 is a flow chart showing a segment playback process.

FIG. 12 is a block diagram showing a digital broadcast televisionreceiver according to an embodiment of the present invention.

FIG. 13 is a block diagram showing an example of a detailedimplementation of a system controller shown in FIG. 12.

FIGS. 14A and 14B are diagrams showing a method of controlling a processso as to provide a decoding time equal to or longer than a minimumnecessary decoding time.

FIG. 15 is a flow chart showing another example of a segment playbackprocess.

FIG. 16 is a flow chart showing, in detail, an example of a process ofsetting a read start position and a read end position.

FIGS. 17A and 17B are diagrams showing examples of data broadcasttogether with a video/audio stream from a broadcast station.

FIG. 18 is a block diagram showing another example of an implementationof a system controller shown in FIG. 2.

FIG. 19 a diagram showing another example of a process of receiving atelevision signal of a program broadcast from a broadcast station andrecording the program.

FIG. 20 is a diagram showing another example of a segment playbackprocess.

FIG. 21 is a flow chart showing another example of a process ofreceiving and recording a content.

FIG. 22 is a flow chart showing another example of a segment playbackprocess.

FIG. 23 is a block diagram showing a terminal device according to anembodiment of the invention.

FIG. 24 is a block diagram showing a server according to an embodimentof the present invention.

FIG. 25 is a block diagram showing a personal computer according to anembodiment of the present invention.

DETAILED DESCRIPTION

The present invention relates to a method, apparatus and program forrecording and playing back content data, a method, apparatus and programfor playing back content data, and a method, apparatus and program forrecording content data. More particularly, the present invention relatesto a method, apparatus and program for recording and playing backcontent data, a method, apparatus and program for playing back contentdata, and a method, apparatus and program for recording content datathat make it possible for a user to view a specified content in a highlyreliable fashion.

A recording and playback apparatus (for example, a digital broadcasttelevision receiver shown in FIG. 2) according to an embodiment of thepresent invention includes first recording means (for example, a contentdata recording unit shown in FIG. 2) that records the content data;record start time information generation means (for example, a recordstart time information generator shown in FIG. 3) for generating, usingreference time information, record start time information (for example,record start time information shown in FIG. 7) indicating timeinformation associated with a record start position of the content datarecorded by the first recording means, playback control table generationmeans (for example, a stream playback control table generator shown inFIG. 3) for generating a playback control table (for example, a streamplayback control table shown in FIG. 3) indicating, for a particularpart of the content data recorded by the first recording means,correspondence between second relative time information indicating arelative time with respect to the record start position of the contentdata and the amount of the content data as measured from the recordstart position, second recording means (for example, metadata recordingunit shown in FIG. 3) for recording playback control information (forexample, content start time information shown in FIG. 7) includingcontent start time information indicating the content start positionusing the reference time information, the record start time informationgenerated by the record start time information generation means, and theplayback control table generated by the playback control tablegeneration means, playback control information reading means (forexample, metadata manager shown in FIG. 3) for reading the content starttime information, the record start time information, and the playbackcontrol table recorded by the second recording means, relative timeinformation correction means (for example, relative time informationcorrection unit shown in FIG. 3) for correcting the first relative timeinformation specifying a playback position of the content data, based onthe content start time information and the record start time informationread by the playback control information reading means, so as to acquirethe second relative time information, identification means (for example,a metadata manager shown in FIG. 3) for identifying the relativeposition information of the playback position, based on the secondrelative time information acquired via the correction made by therelative time information correction means using the playback controltable read by the playback control information reading means, andplayback means (for example, content data playback unit shown in FIG. 2)for playing back the contend data by reading the content data at theplayback position corresponding to the relative position informationidentified by the identification means.

The recording and playback apparatus may further include receiving means(for example, a receiving unit shown in FIG. 2) for receiving thecontent data and the content start time information broadcast by abroadcast station.

The recording and playback apparatus may further include communicationmeans (for example, a communication unit shown in FIG. 23) forcommunicating with another apparatus to acquire the content data and thecontent start time information transmitted from that apparatus.

The recording and playback apparatus may further include output means(for example, an output unit shown in FIG. 2) for outputting the contentdata played back by the playback means.

The content data may be in a form compressed according to the MPEGstandard, the playback control table generation means may generate theplayback control table indicating the correspondence between the secondrelative time information and the relative position information for afirst picture of each GOP of the content data (for example, in steps S7to S9 shown in FIG. 10), and, based on the playback control table, theidentification means may redefine the playback position at the firstpicture of a GOP including the playback position and may identify therelative position information of the first picture (for example, in stepS33 or S36 in FIG. 11).

The content data may be in a form encrypted according to a predeterminedmethod, and the recording and playback apparatus may further comprisedecoding means (for example, a decoder shown in FIG. 12) for decodingthe encrypted content data, and playback position setting means (forexample, read start/end position setting unit shown in FIG. 13) forsetting the playback position such that the playback position provides aperiod of time equal to or longer than a period of time necessary forthe decoding means to complete the process of decoding the encryptedcontent data.

A recording and playback method according to an embodiment of thepresent invention includes the steps of recording the content data (forexample, in step S5 shown in FIG. 10), generating (for example, in stepS6 shown in FIG. 10), using reference time information, record starttime information indicating time information associated with a recordstart position of the content data recorded in the content datarecording step, generating (for example, in step S9 shown in FIG. 10) aplayback control table indicating, for a particular part of the contentdata recorded in the content data recording step, correspondence betweensecond relative time information indicating a relative time with respectto the record start position of the content data and the amount of thecontent data as measured from the record start position, recording (forexample, in steps S4, S6, and S12 shown in FIG. 11) playback controlinformation including content start time information indicating thecontent start position using the reference time information, the recordstart time information generated in the record start time informationgeneration step, and the playback control table generated in theplayback control table generation step, reading (for example, in stepS31 shown in FIG. 11) the content start time information, the recordstart time information, and the playback control table recorded in theplayback control information recording step, correcting (for example, instep S34 or S37 shown in FIG. 11) the first relative time informationspecifying a playback position of the content data, based on the contentstart time information and the record start time information read in theplayback control information reading step, so as to acquire the secondrelative time information, identifying (for example, in step S35 or S38shown in FIG. 11) the relative position information of the playbackposition, based on the second relative time information acquired in therelative time information correction step using the playback controltable read in the playback control information reading step, and playingback (for example, in step S39 shown in FIG. 11) the contend data byreading the content data at the playback position corresponding to therelative position information identified in the identification step.

A program according to an embodiment of the present invention includesthe steps of recording the content data (for example, in step S5 shownin FIG. 10), generating (for example, in step S6 shown in FIG. 10),using reference time information, record start time informationindicating time information associated with a record start position ofthe content data recorded in the content data recording step, generating(for example, in step S9 shown in FIG. 10) a playback control tableindicating, for a particular part of the content data recorded in thecontent data recording step, correspondence between second relative timeinformation indicating a relative time with respect to the record startposition of the content data and the amount of the content data asmeasured from the record start position, recording (for example, insteps S4, S6, and S12 shown in FIG. 11) playback control informationincluding content start time information indicating the content startposition using the reference time information, the record start timeinformation generated in the record start time information generationstep, and the playback control table generated in the playback controltable generation step, reading (for example, in step S31 shown in FIG.11) the content start time information, the record start timeinformation, and the playback control table recorded in the playbackcontrol information recording step, correcting (for example, in step S34or S37 shown in FIG. 11) the first relative time information specifyinga playback position of the content data, based on the content start timeinformation and the record start time information read in the playbackcontrol information reading step, so as to acquire the second relativetime information, identifying (for example, in step S35 or S38 shown inFIG. 11) the relative position information of the playback position,based on the second relative time information acquired in the relativetime information correction step using the playback control table readin the playback control information reading step, and playing back (forexample, in step S39 shown in FIG. 11) the contend data by reading thecontent data at the playback position corresponding to the relativeposition information identified in the identification step.

A playback apparatus (for example, a playback unit shown in FIG. 2)includes playback control information reading means (for example,metadata manager shown in FIG. 3) for reading, from a recording medium,content start time information indicating, using reference timeinformation, time information associated with a start position of acontent, record start time information indicating, using the referencetime information, time information associated with a record startposition of the content data, and a playback control table indicating,for a particular part of the content data recorded on the recordingmedium, correspondence between second relative time informationindicating a relative time with respect to the record start position ofthe content data and the amount of the content data as measured from therecord start position, relative time information correction means (forexample, relative time information correction unit shown in FIG. 3) forcorrecting the first relative time information specifying a playbackposition of the content data, based on the content start timeinformation and the record start time information read by the playbackcontrol information reading means, so as to acquire the second relativetime information, identification means (for example, a metadata managershown in FIG. 3) for identifying the relative position information ofthe playback position, based on the second relative time informationacquired via the correction made by the relative time informationcorrection means using the playback control table read by the playbackcontrol information reading means, and playback means (for example,content data playback unit shown in FIG. 2) for playing back the contenddata by reading the content data at the playback position correspondingto the relative position information identified by the identificationmeans.

The playback apparatus may further include output means (for example, anoutput unit shown in FIG. 2) for outputting the content data played backby the playback means.

In the playback apparatus, the content data may be in a form compressedaccording to the MPEG standard, and, based on the playback control tableindicating the correspondence between the second relative timeinformation and the relative position information for the first pictureof each GOP of the content data, the identification means may redefinethe playback position at the first picture of a GOP including theplayback position and may identify the relative position information ofthe first picture (for example, in step S33 or S36 in FIG. 11).

In the playback apparatus, the content data may be in a form encryptedaccording to a predetermined method, and the playback apparatus mayfurther comprise decoding means (for example, a decoder shown in FIG.12) for decoding the encrypted content data, and playback positionsetting means (for example, read start/end position setting unit shownin FIG. 13) for setting the playback position such that the playbackposition provides a period of time equal to or longer than a period oftime necessary for the decoding means to complete the process ofdecoding the encrypted content data.

A playback method according to an embodiment of the present inventionincludes the steps of reading (for example, in step S31 shown in FIG.11), from a recording medium, content start time information indicating,using reference time information, time information associated with astart position of a content, record start time information indicating,using the reference time information, time information associated with arecord start position of the content data, and a playback control tableindicating, for a particular part of the content data recorded on therecording medium, correspondence between second relative timeinformation indicating a relative time with respect to the record startposition of the content data and the amount of the content data asmeasured from the record start position, correcting (for example, instep S34 or S37 shown in FIG. 11) the first relative time informationspecifying a playback position of the content data, based on the contentstart time information and the record start time information read in theplayback control information reading step, so as to acquire the secondrelative time information, identifying (for example, in step S35 or S38shown in FIG. 11) the relative position information of the playbackposition, based on the second relative time information acquired in therelative time information correction step using the playback controltable read in the playback control information reading step, and playingback (for example, in step S39 shown in FIG. 11) the contend data byreading the content data at the playback position corresponding to therelative position information identified in the identification step.

A program according to an embodiment of the present invention includesthe steps of reading (for example in step S31 shown in FIG. 11), from arecording medium, content start time information indicating, usingreference time information, time information associated with a startposition of a content, record start time information indicating, usingthe reference time information, time information associated with arecord start position of the content data, and a playback control tableindicating, for a particular part of the content data recorded on therecording medium, correspondence between second relative timeinformation indicating a relative time with respect to the record startposition of the content data and the amount of the content data asmeasured from the record start position, correcting (for example, instep S34 or S37 shown in FIG. 11) the first relative time informationspecifying a playback position of the content data, based on the contentstart time information and the record start time information read in theplayback control information reading step, so as to acquire the secondrelative time information, identifying (for example, in step S35 or S38shown in FIG. 11) the relative position information of the playbackposition, based on the second relative time information acquired in therelative time information correction step using the playback controltable read in the playback control information reading step, and playingback (for example, in step S39 shown in FIG. 11) the contend data byreading the content data at the playback position corresponding to therelative position information identified in the identification step.

A recording apparatus according to an embodiment of the presentinvention includes first recording means (for example, a content datarecording unit shown in FIG. 2) for recording the content data, recordstart time information generation means (for example, a record starttime information generator shown in FIG. 3) for generating, usingreference time information, record start time information indicatingtime information associated with a record start position of the contentdata recorded by the first recording means, playback control tablegeneration means (for example, a stream playback control table generatorshown in FIG. 3) for generating a playback control table indicating, fora particular part of the content data recorded by the first recordingmeans, correspondence between second relative time informationindicating a relative time with respect to the record start position ofthe content data and the amount of the content data as measured from therecord start position, second recording means (for example, metadatarecording unit shown in FIG. 3) for recording playback controlinformation including content start time information indicating thecontent start position using the reference time information, the recordstart time information generated by the record start time informationgeneration means, and the playback control table generated by theplayback control table generation means.

The recording apparatus may further include receiving means (forexample, a receiving unit shown in FIG. 2) for receiving the contentdata and the content start time information broadcast by a broadcaststation.

The recording apparatus may further include communication means (forexample, a communication unit shown in FIG. 23) for communicating withanother apparatus to acquire the content data and the content start timeinformation transmitted from that apparatus.

A recording method according to an embodiment of the present inventionincludes the steps of recording the content data (for example, in stepS5 shown in FIG. 10), generating (for example, in step S6 shown in FIG.10), using reference time information, record start time informationindicating time information associated with a record start position ofthe content data recorded in the content data recording step, generating(for example, in step S9 shown in FIG. 10) a playback control tableindicating, for a particular part of the content data recorded in thecontent data recording step, correspondence between second relative timeinformation indicating a relative time with respect to the record startposition of the content data and the amount of the content data asmeasured from the record start position, recording (for example, insteps S4, S6, and S12 shown in FIG. 11) playback control informationincluding content start time information indicating the content startposition using the reference time information, the record start timeinformation generated in the record start time information generationstep, and the playback control table generated in the playback controltable generation step.

A program according to an embodiment of the present invention includesthe steps of recording the content data (for example, in step S5 shownin FIG. 10), generating (for example, in step S6 shown in FIG. 10),using reference time information, record start time informationindicating time information associated with a record start position ofthe content data recorded in the content data recording step, generating(for example, in step S9 shown in FIG. 10) a playback control tableindicating, for a particular part of the content data recorded in thecontent data recording step, correspondence between second relative timeinformation indicating a relative time with respect to the record startposition of the content data and the amount of the content data asmeasured from the record start position, recording (for example, insteps S4, S6, and S12 shown in FIG. 11) playback control informationincluding content start time information indicating the content startposition using the reference time information, the record start timeinformation generated in the record start time information generationstep, and the playback control table generated in the playback controltable generation step.

A recording and playback apparatus (for example, a digital broadcasttelevision receiver shown in FIG. 2) includes first recording means (forexample, a content data recording unit shown in FIG. 2) for recordingthe content data, record start time information generation means (forexample, a record start time information generator shown in FIG. 3) forgenerating, using reference time information, record start timeinformation indicating time information associated with a record startposition of the content data recorded by the first recording means,second recording means (for example, metadata recording unit shown inFIG. 3) for recording playback control information including contentstart time information indicating the content start position using thereference time information, the record start time information generatedby the record start time information generation means, and a playbackcontrol table indicating, for a particular part of the content datarecorded by the first recording means, correspondence between therelative time information and first relative position informationindicating the amount of data as measured from the start of the content,playback control information reading means (for example, metadatamanager shown in FIG. 3) for reading the content start time information,the record start time information, and the playback control tablerecorded by the second recording means, offset value calculation means(for example, an offset value calculator shown in FIG. 18) forcalculating an offset value to be used in correction of the firstrelative position information, using the content start time information,the record start time information, and the playback control table readby the playback control information reading means, identification means(for example, a metadata manager shown in FIG. 3) for identifying thefirst relative position information associated with the playbackposition specified by the relative time information, based on theplayback control table read by the playback control information readingmeans, relative position information correction means (for example, arelative position information correction unit shown in FIG. 18) forcorrecting the first relative position information identified by theidentification means, based on the offset value calculated by the offsetvalue calculation means, to acquire the second relative positioninformation indicating the amount of data as measured from the recordstart position of the content data recorded by the first recordingmeans, and playback means (for example, a content data playback unitshown in FIG. 2) for playing back the content data by reading thecontent data at the playback position, based on the second relativeposition information acquired via the correction process performed bythe relative position information correction means.

A recording and playback method according to an embodiment of thepresent invention includes the steps of recording the content data (forexample, in step S115 shown in FIG. 21), generating (for example, instep S116 shown in FIG. 21), using reference time information, recordstart time information indicating time information associated with arecord start position of the content data recorded in the content datarecording step, recording (for example, in steps S114 and S116 shown inFIG. 21) playback control information including content start timeinformation indicating the content start position using the referencetime information, the record start time information generated in therecord start time information generation step, and a playback controltable indicating, for a particular part of the content data recorded inthe content data recording step, correspondence between the relativetime information and first relative position information indicating theamount of data as measured from the start of the content, reading (forexample, in step S131 shown in FIG. 22) the content start timeinformation, the record start time information, and the playback controltable recorded in the playback control information recording step,calculating (for example, in step S134 shown in FIG. 22) an offset valueto be used in correction of the first relative position information,using the content start time information, the record start timeinformation, and the playback control table read in the playback controlinformation reading step, identifying (for example, in step S136 or S139shown in FIG. 22) the first relative position information associatedwith the playback position specified by the relative time information,based on the playback control table read in the playback controlinformation reading step, correcting (for example, in step S137 or S140shown in FIG. 22) the first relative position information identified inthe identification step, based on the offset value calculated in theoffset value calculation step, to acquire the second relative positioninformation indicating the amount of data as measured from the recordstart position of the content data recorded in the content datarecording step, and playing back (for example, in step S141 shown inFIG. 22) the content data by reading the content data at the playbackposition, based on the second relative position information acquired inthe relative position information correction step.

A program according to an embodiment of the present invention includesthe steps of recording the content data (for example, in step S115 shownin FIG. 21), generating (for example, in step S116 shown in FIG. 21),using reference time information, record start time informationindicating time information associated with a record start position ofthe content data recorded in the content data recording step, recording(for example, in steps S114 and S116 shown in FIG. 21) playback controlinformation including content start time information indicating thecontent start position using the reference time information, the recordstart time information generated in the record start time informationgeneration step, and a playback control table indicating, for aparticular part of the content data recorded in the content datarecording step, correspondence between the relative time information andfirst relative position information indicating the amount of data asmeasured from the start of the content, reading (for example, in stepS131 shown in FIG. 22) the content start time information, the recordstart time information, and the playback control table recorded in theplayback control information recording step, calculating (for example,in step S134 shown in FIG. 22) an offset value to be used in correctionof the first relative position information, using the content start timeinformation, the record start time information, and the playback controltable read in the playback control information reading step, identifying(for example, in step S136 or S139 shown in FIG. 22) the first relativeposition information associated with the playback position specified bythe relative time information, based on the playback control table readin the playback control information reading step, correcting (forexample, in step S137 or S140 shown in FIG. 22) the first relativeposition information identified in the identification step, based on theoffset value calculated in the offset value calculation step, to acquirethe second relative position information indicating the amount of dataas measured from the record start position of the content data recordedin the content data recording step, and playing back (for example, instep S141 shown in FIG. 22) the content data by reading the content dataat the playback position, based on the second relative positioninformation acquired in the relative position information correctionstep.

The present invention is described in further detail below withreference to embodiments in conjunction with the accompanying drawings.

FIG. 2 shows a digital broadcast television receiver according to anembodiment of the present invention.

This digital broadcast television receiver 31 is adapted to receive adigital broadcast service provided by a broadcast station (not shown).That is, the digital broadcast television receiver 31 is configured toreceive a digital television signal broadcast from the broadcast stationand display a program according to the received television signal.

The digital broadcast television receiver 31 includes a recording unit41 configured to receive broadcast digital television signal and recordsit as content data on a recording medium, and a playback unit 42configured to read the content data recorded on the recording medium,plays it back, and outputs it.

More specifically, the digital broadcast television receiver 31 includesan antenna 51, a receiving unit 52, a demultiplexer 53, a content datarecording unit 54, a content data playback unit 55, an output unit 56, asystem controller 61, and an operation control unit 62.

The recording unit 41 includes the antenna 51, the receiving unit 52,the demultiplexer 53, the content data recording unit 54, the systemcontroller 61, and the operation control unit 62. The playback unit 42includes the demultiplexer 53, the content data recording unit 54, thecontent data playback unit 55, the output unit 56, the system controller61, and the operation control unit 62.

The receiving unit 52 receives digital television signals broadcast frombroadcast stations (not shown) via the antenna 51. The receiving unit 52has a digital broadcast tuner (not shown) that controls a receivingfrequency band such that a television signal broadcast from a particularbroadcast station is selected from the plurality of television signalsis extracted and furthermore broadcast data is extracted from thetelevision signal. The resultant extracted broadcast data is supplied toa demultiplexer (DEMUX) 53.

The demultiplexer 53 extracts image data 71, audio data 72, and GUI(Graphical User Interface) data 73 from the supplied broadcast data andsupplies the extracted data to a content data playback unit 55.

The image data 71 and the audio data 72 are in the form of compresseddata in accordance with, for example, the MPEG2-TS (Moving PictureExperts Group 2-Transport Stream). The GUI data 73 includes, forexample, text data, still image data, and/or script data, which areoutput as GUI images together with a content image and/or a voice/sound.The GUI data 73 may also be in the form of compressed data according toa particular method.

When the digital broadcast television receiver 31 records a program, thedemultiplexer 53 supplies the image data 71, the audio data 72, and theGUI data 73 to the content data recording unit 54 to record them. Thedemultiplexer 53 also supplies various control metadata included in thebroadcast data to the system controller 61.

The content data recording unit 54 includes, for example, ahigh-capacity storage medium such as a hard disk and a control mechanismfor controlling the storage medium, and the content data recording unit54 records the image data 71, the audio data 72, and the GUI data 73supplied from the demultiplexer 53. These data may be separatelyrecorded in different files or recorded in a multiplexed form in asingle file.

The content data playback unit 55 reproduces image data and audio datato be output by performing a reproducing process including adecompression process and a correction process on the image data 71, theaudio data 72, and the GUI data 73 supplied from the demultiplexer 53.The reproduced image data and audio data are supplied to the output unit56. The content data playback unit 55 includes an image data playbackunit 81, an audio data playback unit 82, a GUI data playback unit 83,and a mixer 84. The image data playback unit 81 performs a reproducingprocess on the image data supplied from the demultiplexer 53 andsupplies the resultant reproduced image data to the mixer 84. The audiodata playback unit 82 performs a reproducing process on the audio datasupplied from the demultiplexer 53 and supplies the resultant reproducedaudio data to the output unit 56. The GUI playback unit 81 performs areproducing process on the GUI data supplied from the demultiplexer 53and supplies the resultant reproduced GUI data to the mixer 84. Themixer 84 mixes the image data supplied from the image data playback unit81 and the GUI data supplied from the GUI data playback unit 83, andmixer 84 supplies the resultant mixed image data to the output unit 56.

The output unit 56 includes, for example, a display such as a CRT or anLCD (not shown) for displaying an image and a speaker (not shown) foroutputting a sound/voice. The output unit 56 may have an external outputterminal via which to output the image data and the audio data to theoutside of the digital broadcast television receiver 31.

The system controller 61 includes a CPU (Central Processing Unit), a ROM(Read Only Memory), and a RAM (Random Access Memory). In accordance witha command input via the operation control unit 62 by a user, the systemcontroller 61 controls the entire digital broadcast television receiver31 including the receiving unit 52, the demultiplexer 53, the contentdata recording unit 54, the content data playback unit 55, and theoutput unit 56. The operation control unit 62 includes input devicessuch as various switches or levers. If a user inputs information byoperating one or more input devices, the operation control unit 62supplies the input information to the system controller 61.

FIG. 3 is a block diagram showing an example of a detailedimplementation of the system controller 61 shown in FIG. 2.

As shown in FIG. 3, the system controller 61 includes a receivecontroller 91, a write controller 92, a read controller 93, a playbackcontroller 94, an output controller 95, a metadata recording unit 96, ametadata manager 101, a content metadata updating unit 111, a recordstart time information generator 112, a relative time informationgenerator 113, a stream playback control table generator 114 and arelative time information correction unit 115.

The receive controller 91 controls the receiving unit 52 in accordancewith a command input by a user by operating the operation control unit62. The receive controller 91 controls a tuner disposed in the receivingunit 52 to receive a television signal with a frequency specified by theuser.

The write controller 92 controls the demultiplexer 53 and the contentdata recording unit 54 to write a content (program) data. The readcontroller 93 controls the demultiplexer 53 and the content datarecording unit 54 to read a content (program) data. The playbackcontroller 94 controls the content data playback unit 55 to play backcontent data. The output controller 95 controls the output unit 56 tooutput content data.

The read controller 93 controls the content data recording unit 54 toread content data recorded in the content data recording unit 54 from aread start position and supply the read content data to thedemultiplexer 53. The read controller 93 also controls the demultiplexer53 to divide the content data into the image data 71, the audio data 72,and the GUI data 73, and supply them to the content data playback unit55. The playback controller 94 controls the content data playback unit55 to play back the supplied data starting from a playback startposition, and supply the played-back content to the output unit 56. Theoutput controller 95 controls the output unit 56 to output the content.

At a playback end position, the playback controller 94 also controls thecontent data playback unit 55 to end the playback of the content, andthe output controller 95 controls the output unit 56 to end theoutputting of the content. If the playback and outputting of the contentare ended, the read controller 93 controls the content data recordingunit 54 to end the reading of the content data at a content read endposition>.

The metadata recording unit 96 includes, for example, a storage mediumsuch as a hard disk or a flash memory and a control mechanism forcontrolling the storage medium, and the metadata recording unit 96records various metadata supplied from the demultiplexer 53 via themetadata manager 101. For example, the metadata recording unit 96records content metadata 121, segment metadata 122, stream playbackcontrol table 123 and other associated meta data 124. The details ofthese data will be described later.

The metadata manager 101 manages control metadata based on which tomanage the content data. For example, the metadata manager 101 suppliesmetadata received from the demultiplexer 53 to the metadata recordingunit 96 to record it therein. The metadata manager 101 also suppliesmetadata to the content metadata updating unit 111, the record starttime information generator 112, the relative time information generator113, the stream playback control table generator 114, and/or therelative time information correction unit 115, as required, and themetadata manager 101 supplies metadata received from some of the contentmetadata updating unit 111, the record start time information generator112, the relative time information generator 113, the stream playbackcontrol table generator 114, and/or the relative time informationcorrection unit 115 to the metadata recording unit 96 to record themetadata therein. Depending on the content of the metadata, the metadatamanager 101 controls the write controller 92 or the read controller 93to read or write content data.

Based on the information supplied from the metadata manager 101, thecontent metadata updating unit 111 updates the content metadata 121 byadding information associated with a record start position of contentdata to the content metadata 121.

The record start time information generator 112 generates record starttime information indicating a record start time of content data andsupplies it to the metadata manager 101. Based on the informationsupplied from the metadata manager 101, the relative time informationgenerator 113 generates relative time information indicating a relativetime with reference to the record start time and supplies it to themetadata manager 101. The stream playback control table generator 114generates a stream playback control table 123 based on the informationsupplied from the metadata manager 101, and supplies it to the metadatamanager 101. The relative time information correction unit 115 correctsthe value of the relative time information based on the informationsupplied from the metadata manager 101 and supplies the correctedrelative time information to the metadata manager 101.

Although in the example described above, the content data recording unit54 for recording content data and the metadata recording unit 96 forrecording metadata are configured as separate units, the content datarecording unit 54 and the metadata recording unit 96 may be integratedin a single recording unit, and content data and metadata may berecorded in the same recording area.

Metadata recorded in the metadata recording unit 96 is described infurther detail below.

FIG. 4 shows an example of a format of the content metadata 121 shown inFIG. 3. As shown in FIG. 4, the content metadata 121 is tableinformation indicating the relationship among a plurality of items ofinformation associated with a content. The content metadata 121 includesprogram guide data 121A indicating content of a program and record startposition information 121B indicating a position, in a recording area ofthe content data recording unit 54, of the start of each content data.In each column of the content metadata 121, one item of information isdescribed. In each row of the content metadata 121, informationassociated with one program (content) is described.

The program guide data 121A includes information associated with aprogram (content) in terms of a title, one or more performers, asummary, and/or a genre. The program guide data 121A is supplied asmetadata of content data from a broadcast station.

The record start position information 121B is information indicating arecording position at which the first data of each program (content)recorded in the content data recording unit 54 is recorded. Thisinformation is supplied from the metadata manager 101 that controls thewrite controller 92.

That is, the content metadata updating unit 111 shown in FIG. 3 updatescontent metadata by adding the record start position information 121Bsupplied from the metadata manager 101 to the program guide data 121Asupplied from a broadcast station, as shown in FIG. 4.

FIG. 5 shows an example of a format of segment metadata 122 shown inFIG. 3.

As shown in FIG. 5, the segment metadata 122 is table informationindicating the relationship among a plurality of items of informationassociated with a segment. In each column of the segment metadata 122,one item of information is described. In each row of the segmentmetadata 122, information associated with one segment is described.

The segment refers to a unit used when a range of content data isrepresented. Each segment may have an arbitrary length, and there is noparticular restriction on the length of the segment. However, ingeneral, each segment has a length which is not equal to the length of aprogram (content). For example, a segment may be a part of a program(content) or may include a range over a plurality of programs. Morespecifically, for example, a segment may include data of a particularscene included in a program (program).

Use of segments as units makes it possible for the digital broadcasttelevision receiver 31 to handle content data in units of segmentsrather than in units of programs (contents).

The segment metadata 122 includes three items, that is, an ID that isidentification information identifying each segment, attributeinformation indicating an attribute of each segment, and relative timeinformation of each segment with respect to the start position of aprogram (content).

The attribute information indicates an attribute of each segment. Forexample, in the case of a news program content, the content is dividedinto segments corresponding to news topics, and attribute informationindicating categories of news, such as “economy” or “sports”, isdescribed for each segment. The relative time information indicates atime as measured with respect to the start of a program, and is used toindicate a temporal position in a program for each segment. The relativetime information may be defined for the start position of each segmentor may be for another position other than the start position, such asthe end position of each segment. The relative time information may be acombination of two or more pieces of time information. For example, therelative time information may be a combination of relative timeinformation indicating the temporal start position of a segment andrelative time information indicating the temporal end position of thesegment.

The segment metadata 122 is supplied as metadata of content data from abroadcast station.

FIG. 6 shows an example of a format of the stream playback control table123 shown in FIG. 3.

The stream playback control table 123 shown in FIG. 6 is tableinformation used to control playback of a content. The stream playbackcontrol table 123 indicates the correspondence between relative timeinformation and relative position information for each GOP (Group OfPictures) including a plurality of pictures of content data decompressedfrom data compressed according to the MPEG2-TS standard.

The relative time information indicates the time (relative time) of thefirst picture of each GOP, as measured with respect to the start ofrecorded data (record start time), and as represented in days, hours,minutes, and seconds or in the number of frames (pictures). The relativeposition information indicates the relative position of the firstpicture of each GOP, as measured with respect to the start of recordeddata (record start position), and as represented in bytes (indicatingthe amount of data from the record start position to the first pictureof each GOP).

That is, the stream playback control table 123 is mapping informationindicating the correspondence between the data position of the recordeddata as measured from the start of the recorded data and the recordingposition in the recording area as measured from the first recordingposition. This stream playback control table 123 is referred to whenstream data is played back not in an original order but in a differentorder as in a case in which data is played back in a fast-forward modeor only a particular part of data is played back. The stream playbackcontrol table 123 is generated by the stream playback control tablegenerator 114 shown in FIG. 3.

FIG. 7 shows an example of a format of associated data 124 shown in FIG.3.

The associated data 124 includes metadata associated with content dataother than the above-described metadata. In the example shown in FIG. 7,the associated data 124 includes content start time information (T00)141 and record start time information (T0) 142.

The content start time information (T00) 141 indicates a start time of aprogram (content) using a PTS (Presentation Time Stamp) value, and issupplied as metadata associated with content data from a broadcaststation. The record start time information (T0) 142 indicates a recordstart time of the program (content) data using a PTS value, and isgenerated by the record start time information generator 112 shown inFIG. 3.

PTS refers to a time stamp inserted in each elementary stream with apacket size (a TS packet) by a MPEG-2 encoder so that a decoder canadjust synchronization of elementary streams based on the PTS. The PTSis used to indicate an access unit of video/audio content to be playedback. In the decoder, when the PTS value becomes equal to an STC (SystemTime Clock) value obtained by counting a 27-MHz clock in 43 bits, anaccess unit corresponding to the PTS value is decoded (played back).Note that each TS packet includes a PCR (Program Clock Reference), andthe decoder reproduces the STC from the PCR in the decoding process.

The digital broadcast television receiver 31 shown in FIG. 2 is capableof playing back and outputting content data based on segments in amanner different from a manner in which a program is broadcast from abroadcast station. This playback mode is referred to as a segmentplayback mode.

In the segment playback mode, as described above, content data is playedback in units of segments. In a normal television broadcast mode, atelevision receiver continuously receives video and audio signals andsimply plays back the video and audio signals as received (in a linearmode). In contrast, in the segment playback mode, video and audiosignals of a part of a program are selectively played back (nonlinearly)in accordance with a selection command issued by a viewer. The segmentplayback mode makes it possible for a broadcast station to provide newservices such as a service that allows a user to select one of manytopics of a news program, a service that allows a user to view adigested version of a sport program including only highlight scenes,and/or a service that allows a user to search video database by akeyword for a desired program from a plurality of programs and view onlya desired part of the program in units of segments.

A process performed in the playback mode by the digital broadcasttelevision receiver 31 shown in FIG. 2 is described below. FIG. 8 showsa manner in which a television signal of a program (content) broadcastfrom a broadcast station is received is recorded.

In FIG. 8, a stream resource 151, which is data of a program (content)broadcast from a broadcast station, is received by the receiving unit(FIG. 2) and recorded as a stream resource 152 by the content datarecording unit 54 via the demultiplexer 53 As shown in FIG. 8, there isa difference in temporal position between the stream resource 152 andthe stream resource 151, and there is a corresponding difference incontent. That is, the content start time information (T00) 141indicating the time, in the PTS value, of the start of the streamresource 151 is not equal to the record start time information (T0) 142indicating the time, in the PTS value, of the start of the streamresource 152.

The record start time information (T0) 142 is generated by the recordstart time information generator 112 (FIG. 3) of the system controller61 in response to starting recording the stream resource 152. The streamplayback control table generator 114 of the system controller 61generates a stream playback control table 123 associated with the streamresource 152 (as represented by an arrow 155). In the stream playbackcontrol table 123 associated with the stream resource 152, the relativetime information of the start of a segment N is represented as Tsegn_rec(Tn<Tsegn_rec<Tn+1), and the relative position information isrepresented as Dsegn_rec (Dn<Dsegn_rec<Dn+1).

Now, referring to FIG. 9, a process of playing back a stream resourcerecorded in the above-described manner in the segment playback mode isdescribed.

If a user specifies a segment based on attribute information, themetadata manager 101 examines the segment table to identify the segmentthat corresponds to the specified attribute information. In the exampleshown in FIG. 9, the metadata manager 101 identifies that a segmenthaving an ID of “n” corresponds to attribute information Asegn specifiedby the user. The metadata manager 101 supplies relative time informationTsegn of the identified segment together with the content start timeinformation (T00) 141 and the record start time information (T0) 142 tothe relative time information correction unit 115.

The relative time information correction unit 115 performs a correctionprocess 162 using the relative time information (Tsegn), the contentstart time information (T00) 141, and the record start time information(T0) 142 to produce corrected relative time information (Tsegn_rec).More specifically, the relative time information correction unit 115corrects the relative time information according to the followingequation (1).Tsegn_rec=Tsegn−(T0−T00)  (1)

The corrected relative time information (Tsegn_rec) acquired via thecorrection process 162 is supplied to the metadata manager 101. Themetadata manager 101 examines the stream playback control table 123 todetect relative position information (Dsegn_rec) corresponding to thecorrected relative time information (Tsegn_rec). In the example shown inFIG. 9, as described above with reference to FIG. 8, the relative timeinformation Tsegn_rec is within the range Tn<Tsegn_rec<Tn+1, and thusthe metadata manager 101 identifies the relative time information Tn ofthe start position of a GOP including that position. The metadatamanager 101 reads relative position information Dn corresponding to therelative time information Tn and supplies it to the controller 93 (asshown by an arrow 163), which controls reading of the segment N inaccordance with the supplied information.

Thus, via the process described above, the read controller 93 acquiresthe relative time information with respect to the start position of therecorded stream resource 152 as shown in the uppermost row shown in FIG.9, and the read controller 93 starts reading the segment N correctlyfrom the start position of the segment N.

The metadata manager 101 also supplies the relative time information(Tsegn) and the content start time information (T00) 141 to the playbackcontroller 94 via the read controller 93 (as shown by an arrow 164). Theplayback controller 94 monitors the PTS of the content data and controlsthe content data playback unit 55 to start playback of the content froma position (playback start position) at which the PTS of the contentdata is equal to Tsegn+T00. The output controller 95 controls the outputunit 56 to output the played-back content. Thus, the playback controller94 and the output controller 95 can play back and output the segment Nprecisely from the start position thereof thereby allowing a user toview the segment N.

The read controller 93, the playback controller 94, and the outputcontroller 95 control ending of reading, playing-back, and outputting ofthe content such that the playback and outputting of the segment N areended precisely at the end position of the segment N, and subsequentlythe reading of the segment N is also ended.

Thus, a user can view the program precisely from the start to the end ofthe segment N.

The processing flow is described in further detail below with referenceto specific examples.

First, referring to a flow chart shown in FIG. 10, a process ofreceiving and recording a content is described.

For example, if a user issues a record start command or if apreprogrammed record start time is reached, the system controller 61starts a process of receiving and recording a content.

In a first step S1 in the content receiving and recording process, thereceive controller 91 controls the receiving unit 52 to start receivingcontent data. Under the control of the receive controller 91, thereceiving unit 52 receives television signals via the antenna 51 andextracts program (content) data broadcast from a specified broadcaststation. The extracted program (content) data is supplied to thedemultiplexer 53.

In step S2, the write controller 92 in the system controller 61 controlsthe demultiplexer 53 to extract metadata from the acquired content dataand supply the extracted metadata to the metadata manager 101 in thesystem controller 61. Under the control of the write controller 92, thedemultiplexer 53 supplies the metadata extracted from the content datato the metadata manager 101. If the metadata manager 101 receives themetadata, the metadata manager 101 supplies the received metadata to thecontent metadata updating unit 111. The metadata manager 101 alsoacquires information associated with a record start position of thecontent data corresponding to the metadata from the content datarecording unit 54 via the write controller 92 and supplies the acquiredinformation together with the content metadata to the content metadataupdating unit 111. In step S3, the content metadata updating unit 111updates the content metadata by adding the record position informationof the start of the content data to the content metadata.

If the metadata manager 101 acquires the updated content metadata, thenin step S4, the metadata manager 101 supplies the acquired metadata tothe metadata recording unit 96 to record it therein. In step S5, thewrite controller 92 controls the demultiplexer 53 and the content datarecording unit 54 to start recording the content data including theimage data 71, the audio data 72, and the GUI data 73. Under the controlof the write controller 92, the content data recording unit 54 recordsthe content data supplied from the demultiplexer 53.

In step S6, the record start time information generator 112 detects thePTS value of a picture first recorded in the content data recording unit54 via the metadata manager 101 and the write controller 92, andproduces record start time information 142 based on the detected PTSvalue. The resultant record start time information 142 is supplied tothe metadata manager 101. The metadata manager 101 supplies the receivedrecord start time information 142 to the metadata recording unit 96 torecord it as the associated data 124.

In step S7, the write controller 92 monitors the image data (orinformation associated with it) being recorded by the content datarecording unit 54 to determine whether the current image data beingrecorded is a first picture of a GOP. If it is determined that thecurrent image data is a first picture, then the relative timeinformation generator 113 advances the process to step S8 to producerelative time information with reference to the record start timeinformation. In step S9, the metadata manager 101 acquires the relativetime information from the relative time information generator 113 andalso acquires relative position information with reference to the startposition from the write controller 92, The metadata manager 101 producesthe stream playback control table 123 indicating the correspondencebetween the relative time information and the relative positioninformation. In a case in which there is already an existing streamplayback control table 123, the metadata manager 101 adds theinformation indicating the correspondence to the existing streamplayback control table 123. After step S9 is completed, the metadatamanager 101 advances the process to step S10.

In the case in which it is determined in step S7 that the currentpicture is not the first picture of the GOP, the metadata manager 101advances the process to step S10 without performing steps S8 and S9.

In step S10, the metadata manager 101 determines whether to end theprocess of recording the content data. For example, if the end of theprogram (content) has not yet been reached, and thus if it is determinedthat the recording of the content data should not be ended, the processreturns to step S7 to repeat the above-described process from step S7.

By performing steps S7 to S10 repeatedly, the metadata manager 101produces the stream playback control table 123. If the end of theprogram (content) is reached or a record end command is issued by a userand thus if it is determined in step S10 that the recording of thecontent data should be ended, the system controller 61 advances theprocess to step S11.

In step S11, the receive controller 91 and the write controller 92 endthe receiving and recording of the content data by controlling relatedparts. Thereafter, in step S12, the metadata manager 101 supplies thegenerated stream playback control table 123 to the metadata recordingunit 96 to record it.

If step S12 is completed, the system controller 61 ends the process ofreceiving and recording the content.

By performing the process of receiving and recording the content in theabove-described manner, the digital broadcast television receiver 31acquires, in addition to the information supplied from the broadcaststation, the record start time information 142 and the stream playbackcontrol table 123 associated with the recorded stream source and recordsthe acquired the record start time information 142 and the streamplayback control table 123. This makes it possible for the digitalbroadcast television receiver 31 to precisely present the specifiedcontent to a user.

Next, referring to a flow chart shown in FIG. 11, a segment playbackprocess is described below.

If a user issues a command to play back a specified segment, the systemcontroller 61 performs the segment playback process.

In a first step S31 of the segment playback process, the metadatamanager 101 reads necessary metadata from the metadata recording unit96. In step S32, based on the read content metadata, the metadatamanager 101 identifies the content specified by the user to be playedback and also identifies the position where the content is recorded.

If the content data is identified, then in next step S33, the metadatamanager 101 further identifies the relative time information of thestart of the segment corresponding to the specified attribute, based onthe read segment metadata. If the relative time information of thesegment is identified, the metadata manager 101 supplies the relativetime information, the content start time information 141, and the recordstart time information 142 to the relative time information correctionunit 115. In step S34, based on the content start time information 141and the record start time information 142, the relative time informationcorrection unit 115 corrects the identified relative time information inaccordance with equation (1) described earlier, and returns thecorrected value to the metadata manager 101. If the metadata manager 101receives the corrected relative time information, then in step S35, themetadata manager 101 calculates the read start position based on thestream playback control table 123.

Similarly, in step S36, the metadata manager 101 identifies the relativetime information of the end of the segment corresponding to thespecified attribute, based on the segment metadata, and the metadatamanager 101 supplies the relative time information, the content starttime information 141, and the record start time information 142 to therelative time information correction unit 115. In step S37, based on thecontent start time information 141 and the record start time information142, the relative time information correction unit 115 corrects theidentified relative time information in accordance with equation (1)described earlier, and returns the corrected value to the metadatamanager 101. If the metadata manager 101 receives the corrected relativetime information, then in step S38, the metadata manager 101 calculatesthe read end position based on the stream playback control table 123.

If the read start position and the read end position are determined inthe above-described manner, the read controller 93 acquires theinformation associated with the read start position and the read endposition from the metadata manager 101, and in step S39, the readcontroller 93 controls the demultiplexer 53 and the content datarecording unit 54 to start reading the content data from the read startposition. The read content data is supplied to the content data playbackunit 55.

In step S40, the playback controller 94 controls the content dataplayback unit 55 to monitor the PTS of the content data supplied fromthe demultiplexer 53 and start playback of the content from the playbackstart position (the start of the segment identified in step S33) atwhich the PTS value is equal to Tsegn+T00. The output controller 95controls the output unit 56 to output the played-back content. In stepS41, the playback controller 94 and the output controller 95 end theplaying back and outputting of the content at the playback end positionaccording to the PTS. In step S42, the read controller 93 ends thereading of the content data at the read end position, and ends thesegment playback process.

In the segment playback process, as described above, use of the streamplayback control table 123 associated with the recorded content dataallows the digital broadcast television receiver 31 to correctlyidentify the start position and the end position of the specifiedsegment, start reading the segment including the start and endpositions, end reading the segment at the end position, start playingback and outputting the segment from the beginning of the segment, andend playing back and outputting the segment at the end of the segment,and thus allowing a user to view the exact specified content.

As described above, the digital broadcast television receiver 31generates a stream playback control table 123 associated with recordedcontent data, and plays back a segment based on the stream playbackcontrol table 123. Use of the stream playback control table 123 makes itpossible to easily determine corrected relative time information to beactually employed from relative time information described in a segmentmetadata. It is possible to determine corrected relative timeinformation regardless of whether the record start time is before orafter the content start time. Thus, the digital broadcast televisionreceiver 31 is capable of easily playing back a specified segment.

Content data broadcast from a broadcast station may be in an encryptedform. Some digital broadcast stations broadcast program data in anencrypted form to allow only authorized users to view programs. Thepresent invention is also applicable when broadcast program data is inan encrypted form.

FIG. 12 shows another embodiment of a digital broadcast televisionreceiver according to the present invention. The digital broadcasttelevision receiver 181 shown in FIG. 12 is basically similar instructure to the digital broadcast television receiver 31 except thatthe digital broadcast television receiver 181 additionally includes adecoder 191, a view permission judgment unit 192, and a key extractor193.

In this case, encrypted content data received from a broadcast stationis recorded in the content data recording unit 54. Using a decryptionkey supplied from the key extractor 193, the decoder 191 decryptsencrypted image data 71, audio data 72, and GUI data 73 read from thecontent data recording unit 54. The resultant decrypted image data 71,audio data 72, and GUI data 73 are supplied to the demultiplexer 53.

The encrypted content data supplied from the broadcast station includesa TS packet including an entitlement control message (ECM) includingview entitlement information and a decryption key. If the demultiplexer53 detects an ECM from the content data read from the content datarecording unit 54, the demultiplexer 53 supplies the detected ECM to theview permission judgment unit 192. Based on the view entitlementinformation described in the supplied ECM, the view permission judgmentunit 192 determines whether to permit viewing of the content. If it isdetermined that viewing of the content should be permitted, the viewpermission judgment unit 192 supplies the ECM to the key extractor 193.The key extractor 193 extracts the decryption key from the supplied ECMand supplies the extracted decryption key to the decoder 191. Thedecoder 191 decrypts the encrypted content data using the decryption keyand supplies the decrypted content data to the demultiplexer 53.

The system controller 61 has a read start/end position setting unit 201configured to set a data read start position and a data read endposition such that a sufficient processing period time is provided toensure that the sequence of processes described above, that is, the viewentitlement judgment process performed by the view permission judgmentunit 192, the decryption key extraction process performed by the keyextractor 193, and the waiting for a first event of an ECM packet can beperformed during the provided period time (that is, the processingperiod of time is set to be equal to or greater than a time (minimumnecessary decoding time) necessary to complete the sequence of theabove-described processes). When a segment is played back, the readstart/end position setting unit 201 sets the data read start positionand the data read end position depending on the position of the start ofthe segment such that the processing time provided for the decoding ofthe content data is equal to or greater than the minimum necessarydecoding time.

Herein, as shown in FIG. 14A, let us assume that Tsegn_recS andTsegn_recE are respectively given as a playback start position 213 and aplayback end position 214 of a range 212, to be played back, of thestream resource 211. In this case, because Tsegn_recS is after the startposition Tn of a GOP and before Tn+1, and because the period of timefrom Tn to Tsegn_recE (Tsegn_recE−Tn) is greater than the minimumnecessary decoding time (Tdcr) 221, Tn is selected as a decode startposition 231. A decode end position 232 is set at the end position Tm ofthe GOP such that the decode end position 232 is after Tsegn_recE. Thatis, in this example, when the range 212 to be played back is specified,the read start/end position setting unit 201 sets a range 233 to bedecoded from the decode start position 231 to the decode end position232. Note that the decoding range is also set in a similar manner in theprevious examples described above with reference to FIGS. 1 to 11.

More specifically, the read controller 93 controls the reading processsuch that reading of the stream resource 211 is started from the startposition Tn (decode start position 231) of the GOP including theplayback start position 213, and such that decoding is started. Theplayback controller 94 plays back the stream resource 211 decoded in theabove-described manner from the display start position 213, and theoutput controller 95 outputs it. If the display end position 214 isreached in the playback process and the outputting process, the playbackcontroller 94 end the playback process and the output controller 95 endsthe outputting process. The read controller 93 ends the process ofreading and decoding the stream resource 211 at the end position Tm(decode end position 212) of a GOP including the display end position214.

However, when the minimum necessary decoding time (Tdcr) 241 is longerthan the period of time 242 from Tn Tsegn_recE (Tsegn_recE−Tn), if, asshown in FIG. 14B, the decode start position is set at Tn, the decodingprocess cannot be completed within the given period of time before theplayback process starts. In such a case, to avoid the above problem, theread start/end position setting unit 201 sets the decode start position251 at the start position Tn−1 of a previous GOP. That is, in this case,when the playback range 212 is specified, the read start/end positionsetting unit 201 sets a decoding range 253 from a decode start position251 to a decode end position 252 (so as to have a greater range) suchthat the system controller 61 has a sufficient decoding period beforethe playback process starts and thus making it possible to perform theplayback process in a highly reliable fashion.

More specifically, the read controller 93 controls the process such thatreading of the stream resource 211 is started from the start positionTn−1 (decode start position 251) of a GOP immediately previous to a GOPincluding the playback start position 213, and such that decoding isstarted. The playback controller 94 plays back the stream resource 211decoded in the above-described manner from the display start position213, and the output controller 95 outputs it. If the display endposition 214 is reached in the playback process and the outputtingprocess, the playback controller 94 end the playback process and theoutput controller 95 ends the outputting process. The read controller 93ends the process of reading and decoding the stream resource 211 at theend position Tm (decode end position 252) of a GOP including the displayend position 214.

By setting the decoding time to be greater than the minimum necessarydecoding time (Tdcr) depending on the situation in the above-describedmanner, the digital broadcast television receiver 181 can perform theplayback process in a highly reliable manner so as to ensure that a usercan view a specified content.

The segment playback process in such a situation is described in furtherdetail below with reference to a flow chart shown in FIG. 15. In thissegment playback process, the process is performed in a similar manneruntil the step of identifying the position information of the segment asdescribed below with reference to FIG. 11.

In step S61, the metadata manager 101 reads necessary metadata from themetadata recording unit 96. In step S62, based on the read contentmetadata, the metadata manager 101 identify the content specified to beplayed back and also identifies the position where the content isrecorded. In step S63, the metadata manager 101 further identifies therelative time information of the start of the segment corresponding tothe specified attribute, based on the read segment metadata. In stepS64, the relative time information correction unit 115 corrects theidentified relative time information, based on the content start timeinformation 141 and the record start time information 142. In step S65,the metadata manager 101 identifies the record position of the start ofthe specified segment from the corrected relative time information basedon the stream playback control table.

Similarly, in step S66, the metadata manager 101 identifies the relativetime information of the end of the segment corresponding to thespecified attribute, based on the segment metadata. In step S67, therelative time information correction unit 115 corrects the identifiedrelative time information, based on the content start time information141 and the record start time information 142. In step S68, the metadatamanager 101 identifies the record position of the end of the specifiedsegment from the corrected relative time information based on the streamplayback control table.

In step S69, the read start/end position setting unit 201 sets the readstart position and the read end position, as will be described infurther detail later.

In step S70, the read controller 93 controls the demultiplexer 53 andthe content data recording unit 54 to start reading the content datafrom the read start position. The read content data is supplied to thedecoder 191. If the demultiplexer 53 detects an ECM in the suppliedcontent data, the demultiplexer 53 supplies the detected ECM to the viewpermission judgment unit 192. In step S71, based on the supplied ECM,the view permission judgment unit 192 determines whether to permitviewing of the specified content data. If it is determined that viewingshould be permitted, the view permission judgment unit 192 supplies theECM to the key extractor 193. In step S72, the key extractor 193performs a decryption key extraction process to extract a decryption keyfrom the supplied ECM and supplies the extracted decryption key to thedecoder 191. Using a decryption key supplied from the key extractor 193,the decoder 191 decrypts the content data and supplies the decryptedcontent data to the demultiplexer 53. The demultiplexer 53 divides thecontent data into image data, audio data, and GUI data, and supplies theextracted data to the content data playback unit 55.

In step S74, in accordance with the PTS of the content data supplied tothe content data playback unit 55, the playback controller 94 controlsthe playback process such that reading of the content data is startedfrom the playback start position, and the played-back content issupplied to the output unit 56. The output controller 95 controls theoutput unit 56 to output an image and a sound/voice of the content datasupplied from the content data playback unit 55, starting from theplayback start position.

In step S75, If the playback end position is reached in the playbackprocess performed by the content data playback unit 55, the playbackcontroller 94 ends the playback of the content, and the outputcontroller 95 ends the outputting of the content.

In step S76, the read controller 93 controls the content data recordingunit 54 to end the reading of the content data at the read end position,and ends the segment playback process.

Next, referring to a flow chart shown in FIG. 16, the details of thereading start/end position setting process performed in step S69 shownin FIG. 15 are described.

First, in step S91, the read start/end position setting unit 201determines the minimum necessary decoding time, which is necessary forthe decoder 191 to perform the decoding process. Thereafter, in stepS92, the read start/end position setting unit 201 determines whether theperiod (Tsegn_recE−Tn) from the first picture of a GOP including thecorrected start of the segment to the corrected start of the segment isshorter than the minimum necessary decoding time (Tdcr).

If it is determined that the period (Tsegn_recE−Tn) from the firstpicture of a GOP including the corrected start of the segment to thecorrected start of the segment is shorter than the minimum necessarydecoding time (Tdcr), the read start/end position setting unit 201advances the process to step S93. In step S93, the read start/endposition setting unit 201 sets the read start position at the firstpicture of a GOP immediately previous to the GOP including the correctedstart of the segment. In step S94, the read start/end position settingunit 201 sets the read end position at the last picture of a GOPincluding the corrected end of the segment. If the read end position isset, the read start/end position setting process is completed, and theprocess returns to step S70 shown in FIG. 15.

In the case in which it is determined in step S92 in FIG. 16 that theperiod (Tsegn_recE−Tn) from the first picture of a GOP including thecorrected start of the segment to the corrected start of the segment isequal to or longer than the minimum necessary decoding time (Tdcr), theread start/end position setting unit 201 advances the process to stepS95. In step S95, the read start/end position setting unit 201 sets theread start position at the first picture of a GOP including thecorrected start of the segment. If step S95 is completed, the readstart/end position setting unit 201 advances the process to step S94 tofurther perform the process.

As described above, when content data is in an encrypted form, bycontrolling the segment playback process such that a sufficient periodof time is given to perform the decoding process, the system controller61 can perform the playback process in a highly reliable manner suchthat the playback position is precisely controlled thereby ensuring thata user can view a specified content.

In the example described above with reference to FIG. 17A, the digitalbroadcast station 261 provides, together with the video/audio stream271, data 272 including the program guide data 121A, segment metadata122, and the content start time information 141 to the digital broadcasttelevision receiver 31 (or 181). However, data supplies by digitalbroadcast station 261 is not limited to that in this example. Forexample, as shown in FIG. 17B, the data 272 supplied together with thevideo/audio stream 271 from the digital broadcast station 261 mayinclude, in addition the above-described data, the stream playbackcontrol table 123.

In this case, the system controller 61 of the digital broadcasttelevision receiver 31 controls the segment playback process in a mannerdifferent from the manner described above with reference to FIG. 3, and,as shown in FIG. 18, the system controller 61 includes an offset valuecalculator 281 and a relative position information correction unit 282instead of the stream playback control table generator 114 and therelative time information correction unit 115.

The offset value calculator 281 calculates the offset value of theposition information to be used to correct the relative positioninformation in the segment playback process, as will be described infurther detail later. The relative position information correction unit282 corrects the relative position information based on the offset valuecalculated by the offset value calculator 281.

In this case, the digital broadcast television receiver 31 performs thecontent receiving and recording process as described below withreference to FIG. 19 corresponding to FIG. 8.

The digital broadcast television receiver 31 acquires a stream playbackcontrol table 123 from a broadcast station (as shown by an arrow 291).The digital broadcast television receiver 31 also acquires content starttime information (T00) 141 represented using PTS values from thebroadcast station (as shown by an arrow 292). The digital broadcasttelevision receiver 31 records the acquired information in the metadatarecording unit 96. The digital broadcast television receiver 31generates record start time information (T0) 142 represented using PTSvalues when the received stream resource 152 is recorded (as shown by anarrow 293).

That is, in this case, the stream playback control table 123 recorded inthe metadata recording unit 96 includes information associated with thestream resource 151 as of the time when the stream resource 151 isbroadcast. When the timing of starting recording of a stream resource isdifferent from the program start timing of a program, the relative timeinformation described in the stream playback control table 123 is notequal to the relative tine information with respect to the start of thestream resource 152 recorded in the content data recording unit 54.

The segment playback process is controlled as described below withreference to FIG. 20. First, the system controller 61 identifies asegment to be played back, based on a segment table 122 and furtheridentifies a GOP corresponding to the relative time information of thestart of the segment, based on the stream playback control table 123 (asshown by an arrow 301). The system controller 61 further identifies therelative position information Dn of that GOP, based on the streamplayback control table 123. Thereafter, the system controller 61performs an offset value calculation process 302 to calculate the offsetvalue Trec0 using the content start time information 141 and the recordstart time information 142 in accordance with equation (2).Trec0=T0−T00  (2)

The system controller 61 further calculates the relative positioninformation Drec0 corresponding to the offset value Trec0 of therelative time information, based on the stream playback control table123. The system controller 61 then performs a data position correctionprocess 303 to correct the identified relative position information Dnusing the calculated relative position information Drec0 according toequation (3) thereby acquiring corrected relative position informationDn_rec.Dn_rec=Dn−Drec0  (3)

The corrected relative position information Dn_rec indicates therelative position of the start of a GOP including the start of thesegment N, with reference to the start of the recorded stream resource152. The system controller 61 reads the segment N in accordance with thecorrected relative position information Dn_rec (as shown by an arrow304).

As described above, also in the case in which the stream playbackcontrol table 123 is supplied from the broadcast station, by controllingthe playback process in the above-described manner, the systemcontroller 61 can precisely identify the start position of the segment Nand can control the reading process such that the segment N is readexactly from the start position. This makes it possible for the digitalbroadcast television receiver 31 so as to ensure that a user can view aspecified content.

The metadata manager 101 also supplies the relative time information(Tsegn) and the content start time information (T00) 141 to the playbackcontroller 94 via the read controller 93 (as shown by an arrow 305). Theplayback controller 94 controls the content data playback unit 55 tomonitor the PTS of the read content data and start playback of thecontent from a position (playback start position) at which the PTS ofthe content data is equal to Tsegn+T00. The output controller 95controls the output unit 56 to output the played-back content. Thus, theplayback controller 94 can play back the segment N precisely from thestart position and the output controller 95 can output it, therebyallowing a user to view the exact specified content.

The read controller 93, the playback controller 94, and the outputcontroller 95 also control the ending of reading, playback, andoutputting of the content such that playing back and outputting of thesegment N are ended exactly at the specified end position, and then thereading of the content is ended.

Thus, when a user vies the content, the user is allowed to view only theexact segment N from its start to end.

The system controller 61 also controls the end position of the segmentplayback in a similar manner to the start position. That is, the systemcontroller 61 performs a data position correction using the offset valueto obtain corrected relative position information of the last picture ofa GOP including the end position of the segment N.

The process of receiving and recording a content is described further,referring to a flow chart shown in FIG. 21.

In the flow chart shown in FIG. 21, steps S111 to S116 are performed ina similar manner to steps S1 to S6 shown in FIG. 10.

That is, in step S111, as in step S1, the receive controller 91 controlsthe receiving unit 52 to start receiving content data. In step S112, asin step S2, the write controller 92 controls the demultiplexer 53 toextract metadata from the content data supplied from a broadcaststation, and supply it to the metadata manager 101. Note that in thiscase, the metadata includes the stream playback control table 123supplied from the broadcast station.

In step S113, as in step S3, the content metadata updating unit 111updates the content metadata by adding the information indicating theposition (record start position) where the start of the content data isrecorded when the write controller 92 records the content data in thecontent data recording unit 54. In step S114, as in step S4, themetadata manager 101 controls the metadata recording unit 96 to recordsupplied metadata therein. Note that in this case, the metadata recordedby the metadata manager 101 includes the stream playback control table123 supplied from the broadcast station.

In step S115, as in step S5, the write controller 92 controls thedemultiplexer 53 and the content data recording unit 54 to startrecording the content data. In step S116, as in step S6, the recordstart time information generator 112 generates record start timeinformation 142 based on the PTS value of a firstly-recorded picture andstores it in the metadata recording unit 96.

In the process shown in FIG. 21, unlike the process shown in FIG. 10,the system controller 61 does not produce the stream playback controltable 123, and thus steps S7 to S9 in the flow chart shown in FIG. 10are not performed. In step S117, as in step S7, the metadata manager 101determines whether to end the process of recording the content data. Ifit is determined that the process of recording the content data shouldnot be ended, the process remains in this step S117 until it isdetermined that the process of recording the content data should beended. If it is determined in step S117 that the process of recordingthe content data should be ended, the metadata manager 101 advances theprocess to step S118. In step S118, the metadata manager 101 ends thereceiving and recording of the content data, and thus content receivingand recording process is completed.

As can be seen from the above description, the content receiving andrecording process shown in FIG. 21 is simple than the process shown inFIG. 10. This results in a reduction in the processing load imposed onthe system controller 61 during the content receiving and recordingprocess, and thus it becomes possible for the system controller 61 toeasily receive a content and record it.

A segment playback process is described below with reference to a flowchart shown in FIG. 22. First, in step S131, the metadata manager 101reads metadata recorded in the metadata recording unit 96.

After the metadata is read, In step S132, the metadata manager 101identify the content specified by the user to be played back and alsoidentifies the position where the content is recorded, based on the readcontent metadata. In step S133, the metadata manager 101 furtheridentifies the relative time information (Tsegn) of the start of thesegment corresponding to the specified attribute (Asegn), based on theread segment metadata.

In step S134, the offset value calculator 281 calculates the offsetvalue (Tec0) of the relative time information using the content starttime information 141 and the record start time information 142. In stepS135, the metadata manager 101 identifies the offset value (Drec0) ofthe relative position information, based on the stream playback controltable 123. In step S136, the metadata manager 101 further identifies therecord position (Dn) of the start of the specified segment, based on thestream playback control table 123. In step S137, the relative positioninformation correction unit 282 performs a data position correctingprocess using the offset value of the relative position information toobtain a read start position (Dn_rec) of the content data.

Similarly, in step S138, the metadata manager 101 identifies therelative time information of the end of the segment corresponding to thespecified attribute, based on the segment metadata, and in step S139,the metadata manager 101 identifies the record position of the end ofthe specified segment, based on the stream playback control table 123.In step S140, the relative position information correction unit 282calculates the read end position of the content data, using the offsetvalue of the relative position information.

If the read start position and the read end position of the content dataare determined in the above-described manner, the read controller 93then controls the demultiplexer 53 and the content data recording unit54 to start reading the content data from the read start position. Theread content data is supplied to the content data playback unit 55.

In step S142, the playback controller 94 controls the content dataplayback unit 55 to monitor the PTS of the content data supplied fromthe demultiplexer 53 and start playback of the content from the playbackstart position (the start of the segment identified in step S133) atwhich the PTS value is equal to Tsegn+T00. The output controller 95controls the output unit 56 to output the played-back content. In stepS143, the playback controller 94 and the output controller 95 end theplaying back and outputting of the content at the playback end positionaccording to the PTS. In step S144, the read controller 93 ends thereading of the content data at the read end position, and ends thesegment playback process.

As described above, also in the case in which the stream playbackcontrol table 123 is supplied from the broadcast station, by controllingthe playback process in the above-described manner, the systemcontroller 61 can exactly identify the start position of the specifiedsegment N can control the playback process in a highly reliable fashion.This makes it possible for the digital broadcast television receiver 31so as to ensure that a user can view a specified content.

Also in this embodiment, like the embodiment described above withreference to FIGS. 12 to 16, the content data broadcast from thebroadcast station may be in an encrypted form. In this case, the systemcontroller 61 is configured to include a read start/end position settingunit 201 as with the system controller shown in FIG. 3, and the readstart/end position setting unit 201 controls the read start position andthe read end position so as to provide a time equal to or greater thanthe minimum necessary decoding time Tdcr as shown in FIG. 14.

The method of controlling the process can be applied not only to thedecoding process but also to other processes such as a playback processto ensure that processing time becomes equal to or greater than aminimum necessary time thereby ensuring that the processing is performedin a highly reliable manner. In this case, a threshold value by which todetermine a process to be performed next may be arbitrarily set. Aplurality of threshold values may be set.

In the embodiments described above, it is assumed that a broadcaststation provides a terrestrial digital broadcast service to broadcast aprogram, which is received by digital broadcast television receiver 31.Note that the present invention may also be applied to a broadcastservice via cables. Furthermore, the present invention may be appliednot only to broadcast but also to multicast or unicast.

FIG. 23 shows an example of a communication system according to anembodiment of the present invention. In this communication system shownin FIG. 23, a terminal device 331 receives a content transmitted from aserver 362 via a network 361 such as the Internet, and the terminaldevice 331 outputs an image and/or a voice/sound of the content.

As with the digital broadcast television receiver 31, the terminaldevice 331 includes a recording unit 341 and a playback unit 342. Theterminal device 331 is basically similar to the digital broadcasttelevision receiver 31 except that the terminal device 331 includes acommunication unit 352 instead of the antenna 51 and the receiving unit52. That is, the recording unit 341 includes the communication unit 352,a demultiplexer 53, a content data recording unit 54, a systemcontroller 61, and an operation control unit 62. The playback unit 342includes the demultiplexer 53, the content data recording unit 54, acontent data playback unit 55<an output unit 56, the system controller61, and the operation control unit 62.

Also in this terminal device 331, the system controller 61 performs asimilar process to that performed by the system controller 61 of thedigital broadcast television receiver 31. However, in the terminaldevice 331, unlike the digital broadcast television receiver 31 in whichthe receiving unit 52 receives a television signal, the communicationunit 352 communicates with the server 361 to acquire content data. Inthis communication system configured in the above-described manner, theterminal device 331 can provide great advantages similar to thoseprovided by the digital broadcast television receiver 31.

The server may selectively provide only a segment requested by theterminal device.

In this case, as shown in FIG. 24, the server 371 is configured in asimilar manner to the playback unit 42 of the digital broadcasttelevision receiver 31 except that the server 371 includes acommunication unit 381, connected to the network 372, for communicatingwith the terminal device 373 instead of the output unit 56 of thedigital broadcast television receiver 31. The communication unit 381communicates with the terminal device 373 via the network 372 to send arequest from the terminal device 373 to the system controller 61. Inresponse to receiving the request, under the control of the systemcontroller 61, the communication unit 381 acquires the segment data tobe supplied to the terminal device 373 from the content data playbackunit 55 and supplies the segment data to the terminal device 373. In theserver 371, the content data playback unit 55 may be omitted, and thecontent data recorded in the compressed form in the content datarecording unit 54 may be directly supplied to the terminal device 373.

In this case, the server 371 performs the segment playback process in asimilar manner as described above, and thus a further descriptionthereof is omitted herein.

As described above, according to embodiments of the present invention,the television receiver, the terminal device, and/or the server cancorrectly identify the position of the start of a segment N and cancontrol the playback process according to the identified position. Thus,the television receiver, the terminal device, and/or the server cancorrectly output a specified content thereby allowing a user to view theexact specified content.

In the embodiments described above, in the digital broadcast televisionreceiver 31 shown in FIG. 3, the recording unit 41 and the playback unit42 are configured in a single unit. Alternatively, the recording unit 41and the playback unit 42 may be configured in a separate fashion. A partof the recording unit 41 or the playback unit 42 may be separated fromthe other parts. The television receiver, the terminal device, and/orthe server may each include a plurality of apparatus.

In the broadcast systems or the communication systems described above,only one broadcast, one television receiver, one server, and/or oneterminal are shown for the purpose of simplicity. However, there is noparticular restriction on the number of these apparatus/devices, and thesystem usually includes a plurality of these apparatus/devices. Thebroadcast television signal is not limited to the digital signal, butthe broadcast television signal may be in the form of an analog signal.

The sequence of processing steps described above may be performed bymeans of hardware or software. In this case, for example, the digitalbroadcast television receiver 31 shown in FIG. 2, the digital broadcasttelevision receiver 181 shown in FIG. 12, the terminal device 331 shownin FIG. 23, and/or the server 371 shown in FIG. 24 may be implemented ona personal computer such as that shown in FIG. 25.

In FIG. 25, a CPU (Central Processing Unit) 401 of a personal computer400 performs various processes in accordance with a program stored in aROM (Read Only Memory) 402 or in accordance with a program loaded into aRAM (Random Access Memory) 403 from a storage unit 413. The RAM 403 isalso used to store data used by the CPU 401 in the execution of variousprocesses.

The CPU 401, the ROM 402, and the RAM 403 are connected to each othervia a bus 404. The bus 404 is also connected to an input/outputinterface 410.

The input/output interface 410 is also connected to an input unit 411including a keyboard, mouse, and the like, an output unit 412 includinga display such as a CRT or a LCD and a speaker, a storage unit 413 suchas a hard disk, and a communication unit 414 such as a modem. Thecommunication unit 414 serves to perform communication via a networksuch as the Internet.

Furthermore, the input/output interface 410 is also connected to a drive415, as required. A removable storage medium 421 such as a magneticdisk, an optical disk, a magnetooptical disk, or a semiconductor memoryis mounted on the drive 415 as required, and a computer program is readfrom the removable storage medium 421 and installed into the storageunit 413, as required.

When the processing sequence is executed by software, a program formingthe software may be installed from a storage medium or via a networkonto a computer.

An example of such a storage medium usable for the above purpose is aremovable medium, such as the removable medium 421 shown in FIG. 25, onwhich a program is stored and which is supplied to a user separatelyfrom a computer. Specific examples include a magnetic disk (such as afloppy disk), an optical disk (such as a CD-ROM (Compact Disk-Read OnlyMemory) and a DVD (Digital Versatile Disk)), a magnetooptical disk (suchas an MD (Mini-Disk, trademark)), and a semiconductor memory. A programmay also be supplied to a user by preinstalling it on a built-in ROM 402or a storage unit 413 such as a hard disk disposed in the computer.

In the present description, the steps described in the program stored inthe storage medium may be performed either in time sequence inaccordance with the order described in the program or in a parallel orseparate fashion.

In the present description, the term “system” is used to describe thewhole of a plurality of apparatus.

It should be understood by those skilled in the art that variousmodifications, combinations, sub-combinations and alterations may occurdepending on design requirements and other factors insofar as they arewithin the scope of the appended claims or the equivalents thereof.

It should be understood that various changes and modifications to thepresently preferred embodiments described herein will be apparent tothose skilled in the art. Such changes and modifications can be madewithout departing from the spirit and scope of the present subjectmatter and without diminishing its intended advantages. It is thereforeintended that such changes and modifications be covered by the appendedclaims.

1. A recording and playback apparatus for recording content dataincluding a content and playing back the content of the content data ata position specified by first relative time information indicating arelative time with respect to a start position of the content, therecording and playback apparatus comprising: first recording means forrecording the content data; record start time information generationmeans for generating, using reference time information, record starttime information indicating time information associated with a recordstart position of the content data recorded by the first recordingmeans; playback control table generation means for generating a playbackcontrol table indicating, for a particular part of the content datarecorded by the first recording means, correspondence between secondrelative time information indicating a relative time with respect to therecord start position of the content data and the amount of the contentdata as measured from the record start position; second recording meansfor recording playback control information including content start timeinformation indicating the content start position using the referencetime information, the record start time information generated by therecord start time information generation means, and the playback controltable generated by the playback control table generation means; playbackcontrol information reading means for reading the content start timeinformation, the record start time information, and the playback controltable recorded by the second recording means; relative time informationcorrection means for correcting the first relative time informationspecifying a playback position of the content data, based on the contentstart time information and the record start time information read by theplayback control information reading means, so as to acquire the secondrelative time information; identification means for identifying therelative position information of the playback position, based on thesecond relative time information acquired via the correction made by therelative time information correction means using the playback controltable read by the playback control information reading means; andplayback means for playing back the content data by reading the contentdata at the playback position corresponding to the relative positioninformation identified by the identification means.
 2. A recording andplayback apparatus according to claim 1, further comprising receivingmeans for receiving the content data and the content start timeinformation broadcast by a broadcast station.
 3. A recording andplayback apparatus according to claim 1, further comprisingcommunication means for communicating with another apparatus to acquirethe content data and the content start time information transmitted fromthat apparatus.
 4. A recording and playback apparatus according to claim1, further comprising output means for outputting the content dataplayed back by the playback means.
 5. A recording and playback apparatusaccording to claim 1, wherein the content data is in a form compressedaccording to the MPEG standard; the playback control table generationmeans generates the playback control table indicating the correspondencebetween the second relative time information and the relative positioninformation for a first picture of each GOP of the content data; andbased on the playback control table, the identification means redefinesthe playback position at the first picture of a GOP including theplayback position and identifies the relative position information ofthe first picture.
 6. A recording and playback apparatus according toclaim 1, wherein the content data is in a form encrypted according to apredetermined method, and wherein the recording and playback apparatusfurther comprises decoding means for decoding the encrypted contentdata, and playback position setting means for setting the playbackposition such that the playback position provides a period of time equalto or longer than a period of time necessary for the decoding means tocomplete the process of decoding the encrypted content data.
 7. Arecording and playback method for a recording and playback apparatus torecord content data including a content and play back the content of thecontent data at a position specified by first relative time informationindicating a relative time with respect to a start position of thecontent, the method comprising: recording the content data; generating,using reference time information, record start time informationindicating time information associated with a record start position ofthe content data recorded; generating a playback control tableindicating, for a particular part of the content data recorded in thecontent data recording step, correspondence between second relative timeinformation indicating a relative time with respect to the record startposition of the content data and the amount of the content data asmeasured from the record start position; recording playback controlinformation including content start time information indicating thecontent start position using the reference time information, the recordstart time information generated in the record start time informationgeneration step, and the playback control table generated in theplayback control table; reading the content start time information, therecord start time information, and the playback control table;correcting the first relative time information specifying a playbackposition of the content data, based on the content start timeinformation and the record start time information, so as to acquire thesecond relative time information; identifying the relative positioninformation of the playback position, based on the second relative timeinformation acquired in the relative time information correction stepusing the playback control table; and playing back the contend data byreading the content data at the playback position corresponding to therelative position information.
 8. A playback apparatus for playing backcontent data including a content recorded on a recording medium byreading the content data at a position specified by first relative timeinformation indicating a relative time with respect to a start positionof the content, the playback apparatus comprising: playback controlinformation reading means for reading, from the recording medium,content start time information indicating, using reference timeinformation, time information associated with the start position of thecontent, record start time information indicating, using the referencetime information, time information associated with a record startposition of the content data, and a playback control table indicating,for a particular part of the content data recorded on the recordingmedium, correspondence between second relative time informationindicating a relative time with respect to the record start position ofthe content data and the amount of the content data as measured from therecord start position; relative time information correction means forcorrecting the first relative time information specifying a playbackposition of the content data, based on the content start timeinformation and the record start time information read by the playbackcontrol information reading means, so as to acquire the second relativetime information; identification means for identifying the relativeposition information of the playback position, based on the secondrelative time information acquired via the correction made by therelative time information correction means using the playback controltable read by the playback control information reading means; andplayback means for playing back the contend data by reading the contentdata at the playback position corresponding to the relative positioninformation identified by the identification means.
 9. A playbackapparatus according to claim 8, further comprising output means foroutputting the content data played back by the playback means.
 10. Aplayback apparatus according to claim 8, wherein the content data is ina form compressed according to the MPEG standard; and based on theplayback control table indicating the correspondence between the secondrelative time information and the relative position information for thefirst picture of each GOP of the content data, the identification meansredefines the playback position at the first picture of a GOP includingthe playback position and identifies the relative position informationof the first picture.
 11. A playback apparatus according to claim 8,wherein the content data is in a form encrypted according to apredetermined method, and wherein the playback apparatus furthercomprises decoding means for decoding the encrypted content data, andplayback position setting means for setting the playback position suchthat the playback position provides a period of time equal to or longerthan a period of time necessary for the decoding means to complete theprocess of decoding the encrypted content data.
 12. A playback methodfor a playback apparatus to play back content data including a contentrecorded on a recording medium by reading the content data at a positionspecified by first relative time information indicating a relative timewith respect to a start position of the content, the method comprising:reading, from the recording medium, content start time informationindicating, using reference time information, time informationassociated with the start position of the content, record start timeinformation indicating, using the reference time information, timeinformation associated with a record start position of the content data,and a playback control table indicating, for a particular part of thecontent data recorded on the recording medium, correspondence betweensecond relative time information indicating a relative time with respectto the record start position of the content data and the amount of thecontent data as measured from the record start position; correcting thefirst relative time information specifying a playback position of thecontent data, based on the content start time information and the recordstart time information read in the playback control information readingstep, so as to acquire the second relative time information; identifyingthe relative position information of the playback position, based on thesecond relative time information acquired in the relative timeinformation correction step using the playback control table; andplaying back the contend data by reading the content data at theplayback position corresponding to the relative position information.13. A recording and playback apparatus for recording content dataincluding a content and playing back the content of the content data ata position specified by first relative time information indicating arelative time with respect to a start position of the content, therecording and playback apparatus comprising: a first recording unitconfigured to record the content data; a record start time informationgeneration unit configured to generate, using reference timeinformation, record start time information indicating time informationassociated with a record start position of the content data recorded bythe first recording means; a playback control table generation unitconfigured to generate a playback control table indicating, for aparticular part of the content data recorded by the first recordingunit, correspondence between second relative time information indicatinga relative time with respect to the record start position of the contentdata and the amount of the content data as measured from the recordstart position; a second recording unit configured to record playbackcontrol information including content start time information indicatingthe content start position using the reference time information, therecord start time information generated by the record start timeinformation generation unit, and the playback control table generated bythe playback control table generation unit; a playback controlinformation reading unit configured to read the content start timeinformation, the record start time information, and the playback controltable recorded by the second recording unit; a relative time informationcorrection unit configured to correct the first relative timeinformation specifying a playback position of the content data, based onthe content start time information and the record start time informationread by the playback control information reading unit, so as to acquirethe second relative time information; an identification unit configuredto identify the relative position information of the playback position,based on the second relative time information acquired via thecorrection made by the relative time information correction unit usingthe playback control table read by the playback control informationreading unit; and a playback unit configured to play back the contenddata by reading the content data at the playback position correspondingto the relative position information identified by the identificationunit.
 14. A playback apparatus for playing back content data including acontent recorded on a recording medium by reading the content data at aposition specified by first relative time information indicating arelative time with respect to a start position of the content, theplayback apparatus comprising: a playback control information readingunit configured to read, from the recording medium, content start timeinformation indicating, using reference time information, timeinformation associated with the start position of the content, recordstart time information indicating, using the reference time information,time information associated with a record start position of the contentdata, and a playback control table indicating, for a particular part ofthe content data recorded on the recording medium, correspondencebetween second relative time information indicating a relative time withrespect to the record start position of the content data and the amountof the content data as measured from the record start position; arelative time information correction unit configured to correct thefirst relative time information specifying a playback position of thecontent data, based on the content start time information and the recordstart time information read by the playback control information readingunit, so as to acquire the second relative time information; anidentification unit configured to identify the relative positioninformation of the playback position, based on the second relative timeinformation acquired via the correction made by the relative timeinformation correction means using the playback control table read bythe playback control information reading unit; and a playback unitconfigured to play back the contend data by reading the content data atthe playback position corresponding to the relative position informationidentified by the identification unit.